Home base near London

Don't forget to take into consideration what your time is worth, and how much transportation in and out could cost. If it's worth 45 min in and out every day to save some money, fine, but factor in your train or tube costs. (edit - I see Emma beat me to that comment by 10 min while I was typing...lol)

We stay in Chiswick, but only because we have friends there, so free is worth the time and cost. Plus, only 20 min taxi ride to Heathrow.

One time we just overnighted in London before flying to Italy so we didn't want to stay with them for that one night...we stayed at an airbnb less than a 10 min walk to the Oval/Vauxhall tube station - 15 min into Embankment area - for $70 Canadian. This was 2012, his prices are a little higher now (actually, our dollar is worth less now), and it was not a whole apartment, but a spare bedroom...so if you are ok with airbnb, give them a look-see.

We stayed at the Travelodge (Thank you Emma!) and found it to very nice nice! We needed a triple room so we needed to stay at their Southwark location which is across the river to the south. I was hoping for a location closer to sights, but after staying in that location we really liked it. It felt more out of the craziness of London but the tube was just a block away. They have several locations around London. I would totally stay there again. It was about as basic as you could get, but, it was super clean, quiet, had an elevator, air conditioning, they offered breakfast, wifi, early check in, and it was very cheap!! Perfect!

And, by the way, we were there during a tube strike so we walked all the way to Westminster Abby and it was fine. Even walked home from the Tower of London. I thought it would be way too far, but it wasn't.

If your main interest is London, find a cheap B&B in London. As others said, public transport is not cheap, and your time is valuable as you only have X number of days after flying all the way to London.

If you are interested in particular places outside London, that's a different story. For instance, Stonehenge & Avebury were top priority for us, so we stayed in Newbury (Hare & Hounds, not expensive, very convenient). This enabled us to take the train to London for a day's sightseeing and also to easily drive our rental car to Stonehenge, Avebury, and other points of interest in the Salisbury Plain and North Wessex Downs AONB (Area of Outstanding Natural Beauty).

Give this thread a read...

https://community.ricksteves.com/travel-forum/england/the-truth-of-the-tube

Yes, the "truth of the tube" thread cited above is a good rundown of the pluses and minuses of staying outside the city. For me, the convenience of being in London itself is worth the extra cost, up to a point. There are neighborhoods, like Paddington and Earl's Court and south of the river (and I'm sure others) that provide a good balance between cost and convenience.

BTW - if you didn't check out the thread I linked to - it's now gone - it went right off the rails so the webmaster removed it...

Yeah don't recommend it! If you can't afford to visit London, but want to, I'd wait until you have the money if your budget is tight.

Worst case- do a hostel in London.

Its very expensive to go in and out of the city repeatedly. Even outskirts places near Windsor and whatnot would end up running you quite a bit within the course of a week because of the train ticket prices.

Don't believe all the hype that transport costs in London are expensive, they are not, (just don't buy single/return tickets), get an Oyster Card, just like the locals do.

With a pre-paid Oyster Card, the most you pay daily (unlimited London Tube / Bus /Overground/ TLF Rail/ Docklands Light Rail trips) within Zone 1-2 is £6.50 pounds (Oyster Daily Price Cap). Additionally, you can't catch a London bus if you don't have an Oyster Card.

Zones 1-2, extending out from the centre of London, covers a considerable area ( Chiswick to the west / Nth Greenwich to the east / Hampsted to the north / Brixton to the south) the further you stay from the centre of London, the cheaper accommodation is.

The Oyster Daily Price Cap for Zones 1-3 is £7.60 / Zone 1-4 £9.30 / Zone 1-5 £11 / Zone 1-6 £11.80 and that covers just about the whole of Londons Tube network.

You can save yourself 100's of dollars/pounds on accommodations costs staying out of central London and utilising Londons world best and cheap transport, with an Oyster Card.
https://www.londontoolkit.com/briefing/oystercard.htm

Zone 1-2 Tube Approximate Travel Times into London (Oxford Circus, Oxford St)
Chiswick - Oxford Circus: 34 min
Brixton - Oxford Circus: 19 min
Nth Greenwich - Oxford Circus: 29 min
Hampstead - Oxford Circus: 25 min

If you want to stay outside of London, altogether, in some smaller town/village, and travel in (60-90 min fast train), this link will allow you to book UK Advanced train tickets (2 months before travel) when they first go on sale, and when cheap tickets are available e.g : London - Oxford Anytime fare £30.60. Advanced fare £5.50.

I've just returned from 6 months travelling (train) around the UK and Ireland and used this site for all my transport bookings, I saved heaps. However, some rail lines/journeys don't have cheap tickets
https://loco2.com/

The advance tickets outside the Oyster area that Daisy May refers to require you to choose your exact time of travel when you book. I think this would be far too rigid if you are staying outside London as your home base.

Another option is to purchase a weekly season ticket from where you stay into London, which will also include a Travelcard for unlimited local London travel. They can't be booked online, but only at railway stations, and you will probably need a passport-type photo to attach to them.