We will be arriving from Paris by Eurostar and staying in London 5 days, and taking one day trip to Cambridge (King's Cross Station) and then train (Paddington Station) to Heathrow for flight back home. I was thinking about staying in St Pancras to minimalize walking to hotel with luggage from Eurostar. Would a more central location be better for sight seeing?
You have to use transport no matter where you stay because the things you will want to visit are well spread out, like a thin coating of jam on a piece of toast. No matter where you are, you aren't everywhere else.
St Pancras is well located on the Piccadilly Line - no need to get to Paddington for Heathrow, just go on the Piccadilly Line, lifts, or escalators, at both ends of the journey no muss no fuss, and cheap; also on the Circle, Hammersmith and City, Northern, Metropolitan, and Victoria Lines, as well as many bus lines, and the train to Cambridge, and the Thameslink operates like a tube line in central London, too.
So you are very well connected.
What budget are you looking at? There's everything from Travelodge and Premier Inn up to the 5 star Plus hotel on the station. Small no-star to 1 or 2 star B&Bs, too.
Tell us a little about yourself and what you'd like to see....
I stayed at the Renaissance Hotel that is actually in the St Pancras station right at the end of the tracks on my last visit. (Lucky I had enough Marriott points to get a free night.) Very nice hotel, recently redone but retaining a lot of the Victorian charm. I can highly recommend this one. There are a lot of options around the station to choose from, I would not hesitate to stay at any of them but suggest you check online reviews before picking one.
The Tube connections from St Pancras/Kings Cross are excellent. You can get to most any sight you want to see in mere minutes. Just make sure to get an Oyster Card which will save you lots over any other payment option for Tube and bus rides (They are available at any Tube station and you can cash out any remaining value when you get to the airport tube station or any station when you are done riding the Tube). Also, the Tube ride to the airport is really inexpensive (3.10 Pounds on the Oyster Card) and is my preferred way to get to the airport (unless I am dragging tons of bags with me, then it is a taxi or shared shuttle because even the train from Paddington doesn't work well if you have lots of luggage).
Have a great trip!
Haven't stayed there but have looked at the area in the past, and some of the hotels along the Cartwright Gardens crescent seem to get good review (e.g., Judd Hotel). Worth a look see.
Consider hotels around Russell Square. It's on the Piccadilly Line to Heathrow and a short taxi ride from St. Pancras. I've stayed at the Morgan Hotel in Bloomsbury St. (which is not on the Square). It's family-run, literally around the corner from the British Museum, with good bus service and fairly close to the Holburn tube station, with minimal stairs (about 20) to the Piccadilly Line, I'm pretty sure they're down going to Heathrow and up arriving from Heathrow.
Last May, we used The Californian for exactly the same reason - catching the Eurostar. Very functional hotel, small rooms, good front desk staff, no breakfast included. Couple of nice restaurants in the area with a decent pub near by. We came via train from Edinburgh to King Cross so it was very convenient. It was a bit of long walk but we did walk to the hotel from the Trafalgar Sq area. With the efficiency of the tube, I don't know if one location is any better than another except for dead center.
The Alhambra Hotel on Argyle Street is a neat place with breakfast included; just south of both St. Pancras and Kings Cross. Stayed there last October on our way to Edinburgh. Also, McGlynn's Free House pub is around the corner; great local pub with good food.