London

Answer to Q1: Underground Circle line.
See the tube map here: http://content.tfl.gov.uk/standard-tube-map.pdf which will be your most important asset in finding your way around London. Paddington is in square C3, Kings Cross St Pancras in C5, linked by the yellow and light purple lines.
You now need to research what an Oyster Card is, which is what you need to travel by tube, bus or train in London. Your contactless card may also work if you have one.

Q2: The best way to see London is to go around on your own, with a good guide book. Travelling by tube if you want to get somewhere fast, or by bus if you want slower but to see where you are going.
"London Walks" does guided tours on foot which many recommend: http://www.walks.com/

If this is the start of your research, you need to get a good guide book, and understand how the transport system works (start the latter by reading this leaflet: http://content.tfl.gov.uk/visitor-leaflet-welcome-to-london-nov16.pdf ).

You can use this journey planner if you want to go by pubic transport (Tube quickest or bus cheapest).

https://tfl.gov.uk/plan-a-journey/

Or you could hail a cab at Paddington (most expensive).

I also recommend London Walks mentioned above.
Lots of choices so you can see the things that interest you.

I'd also say to take a look at the trip reports on this forum, they were very helpful when planning my trip. I agree with London Walks and a good guide book instead of a tour company. Also, download the City Mapper app, it was great for help using the tube. London is an awesome city, enjoy!

Are you saying that you are currently in London or that you will be in London - if so, when?

Nigel, we will be coming to London in May. We have lots of research to do before then! Any advice will be very welcome!

Emma, I don't know that we will actually be coming from Paddington. It will actually be from wherever we are staying in London. We don't know yet where that will be since we're in the very beginning of planning the trip. It's been several years since we've done a trip on our own rather than a tour. Any advice about anything London would be most helpful! Thanks!

I really like the Premier Inn Hotel chain for travel in U.K. cities. London has several properties. I find them to be a good value and consistently comfortable.

Thank you Carol! I had no ideas at all so now I feel better!

Emma, you are so helpful! We will only be staying a week in London so I see that we will still be missing a lot. I'm ordering guide books to help me along. I feel better now that you've told me that getting around isn't that hard. I wad dazed and confused at first! I may be messaging you when we get there!

Emma can you give me your thoughts on the Britpass? We will be making a brief (2 days) to the Cotswolds. Is the pass worth it? We haven't decided whether to go on our own or use a tour like Viatour.

Brit pass isn’t worth it.

If you desire to see the Cotswolds during your brief stay then train to Morten on the Marsh from London.

Use this forums search engine for further clarity. Type in getting to Cotswolds from London by train.

Oyster card ( get yours there). Use for public transport. Buses, underground ( Tube) and some rail.

I leave today for two weeks in London and have an Oyster Card I got before Prince William and Kate we’re married. Kept it. It’s got a few pounds still on it. Have used it every year since as I return to London as often as I can. I’ll top it up ( add money to it as I also have a 20 pound note left over from my 2017 trip) when I get there. That should keep me on the go during my sojourn.

As offered above the tfl.gov.uk website is helpful.

As far as a local tour company investigate www.walks.com. NOT a tour company persae but loads of great insightful and intriguing walks to take to see things. This trip I’m doing the legal and illegall walk.

PM with questions. Happy to share what I’ve learned about London over the years.

Great city. Don’t be overwhelmed. Be excited!!!

By "Britpass" do you mean Britrail Pass? If so, with the amount of travelling you have said you will throwing most of the value away. Money gone whistling.

It is possible with the education you will get here, especially if you use the search function and read what other people have asked and what the answers were, to spend much much less on train tickets. And other things...

Thank you Claudia! I'm learning - if slowly.

Thank you Nigel. We sure don't want to waste money if we don't need to. You've been very helpful!

Thanks Emma. You've given us some good info. At this moment our travel dates are May 8 -22 so we may miss the bank holidays but maybe not the school ones. If you think of anything more we'd like to hear it!

Lets slow down and do an assessment of priorities.
Who is coming on this trip?
What do you prioritize as things you like to do? The more specific the better.
How long do you have to spend in London?
How many times have you traveled to europe?

Besides me my brother and his wife are going - all of us in our 60's. We will spend a week in London including a couple of days in the Cotswolds. We plan on hitting the main attractions in London due to time restrictions. I've been to Europe 8 times.
Did I cover wheat you need to know!?

Thanks Elodie

That's helpful. Now, why St Pancras - as in your original question? Is this trip part of a longer one - you see how the more you share the better answers we have, and when you don't we have to guess - using Eurostar from St Pancras to mainland Europe? Or are you interested in St Pancras because you want to go to Derby or Nottingham or Sheffield - or somewhere else served by trains from St Pancras? Or maybe you want to get close to the tasty Dishoom restaurant behind the station?

Yes Nigel. I see I was not very complete with my info! So sorry. I asked about St. Pancras because after our week in London we will be going to Paris. Then depending on airfares we will fly home from Paris or come back to London Heathrow.

If you are not familiar with the process, use a multi-destination search function to find air fares into London and home from Paris. These itineraries are not a set of separately booked one-way tickets.

Using google maps type in "London bayswater hotels" which will depict locations of hotels and allow you to move the map around while continuing to scan for hotels. I recommend seeking accomodations which provide a kitchenette so you have a place to prepare breakfasts, light snacks, picnics and store cold drinks. London offers a worldclass metro system offering easy and relatively inexpensive access to the Tube, bus, train stations and boating. Using these modes of public transport is far simpler than conveyed by online directions and keep in mind everyone speaks english so just ask for help.
Walking is to be highly valued as you will keep passing history with every step and be visually delighted.
We highly recommend spending time at Hampton Court and then taking a boat back to London as this provides an opportunity to experince history w a ride on the thames.
Windsor is another not to be missed daytrip accessible by train.
The menu of opportunities is huge and our stringest recommendation is to book online your tickets for each desired destination. Lines will be long and on line purchase helps you avoid wasting HOURS in line.
Keep defining your interests to the forum and you shall receive excellent guidance.

Thank you! We are still exploring options. Open jaw flights are the best at this point but still trying to nail down our itinerary so we can proceed with flights. There is so much to see and do and so little time!