Watch out for Edinburgh - August is the Festival month and you'll pay top wack in accommodation unless you stay outside the city. Tons to do though, and lots of info at:
http://www.edinburgh.org
Why not go to Glasgow - good shopping, nightlife and people too - and make a day trip through to Edinburgh for the shows? Accomm. prices will be less, and there's a load to do there and easy to get to.
Or try South Wales - Straight down the M4, and keep going til you get to St Davids. Tenby, Pendine, Manorbier - all nice to stay at.
On basis you are in London - be a tourist in London too - do the Tower, Buck Palace, Westminster Cathedral, Zoo, etc etc. Its fun listening to the Americans comments on the trips . . . . . . (and others too of course...)
For really good accommodation - see
http://www.farmstayuk.co.uk for a choice of really nice b&b's etc., all over the country in rural settings but nearly all offer more than just sitting looking at a field - use the clickable map to search for an area you want to try and enjoy some quality time.