Hello! I'm in Canada, but have been watching this forum looking for tips for our trip to the UK/France this August. Just as a heads up, most resorts at WDW have rooms that accommodate 5 people just in a regular room or family suite - it is something we are struggling with trying to plan our vacation in the UK/France. We're used to being able to find accommodations for our family of 5 without issue and very inexpensively. It's pretty standard to find rooms or family suites that have 2 queen or double beds plus a single or double pull-out couch. And there are TONS of houses for rent within 4-5 miles of WDW. For example, you can rent a 5 bedroom house with private pool that sleeps 10-14 people for £1100 for a week in August. We rented one in the Windsor Hills development in March and used it as our home base for WDW and Universal before a cruise - it was very close/convenient for both parks.
I'm not sure if you guys have heard of this site or not, but it's a pretty popular one for people from the US and Canada who are looking for money saving tips for Disney and other parks/attractions in Orlando (Universal, LEGOLAND, etc...). It also has tips and coupon codes for car rentals, attraction ticket discounts, shuttles, and all kinds of other trip-related things. Highly recommend it. If you search online for Mousesavers, it should come up (don't think the site is letting me post the website - mousesavers dot com).