I am heading to London in July.

Has anyone stayed in hotel that will accommodate four persons, maybe a flat? I am trying to keep the cost down to 150 pounds a night.

Location is not too important as I heard that the subway runs everywhere.

My boys are 10 and 7.

You'd probably get more bang for your (Canadian) buck with a flat especially with children.

Much less expensive too to have a kitchen where you can keep snacks & breakfast items for the kids plus you'd probably have a washer/dryer.

How many nights will you be staying? I always use London Guest Suites www.londonguestsuites.com but there are other agencies that are also good.

You might have a problem getting connecting rooms or a quad room on Priceline.

You might consider one of the university halls of residence. For example LSE has a few options:

You could get a quad en suite room and breakfast in Bankside House (just behind the Tate Modern) for £99 a night. A flat with five beds at Butlers Wharf close to Tower Bridge)is £151 a night or £999.50 a week.
http://www.lse.ac.uk/collections/vacations/default.htm

We are also going to London this summer with a family of 4. You can check out Premier Inns (from what I understand, they are like Super 8). They have rooms for about 100 pounds/night. Also, you can get a room for 4 at Travelodge for under 100 pounds and if you can get one of their Supersaver rates, you can sometimes get a room for 29 or 49 pounds. I booked a room at the Travelodge Southwark which is opening in May for 29 pounds/night. We figure we will only be in our room to sleep most days, so don't need a lot of extra amenities.

We've stayed several times at the Holiday Inn Mayfair, which is around your price range (it has averaged in the 130's to 140's - I book AAA rate refundable. You can get a lower rate prepay nonrefundable, iirc).

The benefit of this hotel, imo, is the amazing location. Mayfair is a lovely, central neighborhood. The hotel is a few feet from the Green Park tube station, where three lines cross. You can get just about everywhere easily. The bus stop is just as close.

Oops, this may be obvious, but I forgot to say that there are two double/queen beds in the rooms.

If you're staying for 5 plus days I'd second the flat recommendation. It will be a BIG money saver. Some agencies even allow for rentals of 3 days. I've used london guest suites and farnum and christ and can highly recommend both agencies.

The tube does run to a lot of places, but some areas are just more desirable/convenient - it really depends on what your goals are and what you really want to see/do.

Another nod for the Holiday Inn Mayfair, but I also agree that you might find a flat more comfortable if you are staying several days. The issue will be to find an affordable flat in as good/central a location as the HI Mayfair. (also this hotel is fully air-conditioned, which could be a plus)

I just booked a flat through londonguestsuites.com - Others have told me they we happy with their service and their accomodations.

We stayed last week in our first Premier Inn (at LHR)maybe a bit out of central London but I'd check and see if thy had one in zone 1 or 2.

We, as a family of four, were pleased with it. It was roomy enough for all of us (we did only stay one night)and they allowed 4 in a room. Very clean, services in the lobby were excellent and a great price at 85 pounds per night.

The best located Premier Travel Inn is at County Hall next to the London Eye and across the river from Big Ben/Parliament. It shares a bldg w/ the Marriott but does not share the Marriott's river views, or rates.

But that travel Inn is VERY popular and books up pretty much year round at rates now up over £100 a night.

If budget is any consideration, I would strongly suggest renting a flat.In addition to having more room, it's more economical to pick up food supplies at a place like Marks & Spencer's for breakfast and some dinners than trying to eat out.

definitely stay in a flat
we stay at a fraser property in south kensington. lovely neighbourhood, great tube stations nearbye. much roomier than a hotel, breakfast included, quiet and nicely furnished. no downside at all. my kids were 13 and 15 when we were there and it was very appropriate for them. we had a studio initially, and it was big enough for all, but a bit noisy- we got an upgrade to a 2 bdm that was huge- I do not know the regular price of these, but if not much more,it would be well worth the money. but, if it is much more expensive, the studio is still bigger than hotel room would be.
your boys might like to see churchill's war rooms, tower of london etc- london has lots of stuff to offer that is not just museums!