Sweetpea's recommendations are very good.
Our food is fantastic. Its the same as America - if you want to spend $10 on a meal well you get what you pay for basically so don't expect it to be amazing. If on the other hand you are prepared to spend considerably extra (remember everything costs pretty much double here - glass of wine $8-10, house wine $35 etc etc) you can't eat better. I loved being in the States but I still havent eaten anything over there (swith the exception of some of the Mexican places I went to) where it is nearly half as good as here. That said - half our chefs are French and other European so we can't take all the credit. But it just totally gets my goat when people say our food is bad - do your research for the exact area you are going to - Trip Advisor is a good place to start.
I would pick visiting Scotland (Highlands and Edinburgh) or Cornwall over any other part of England to visit and also South Wales for the beautiful beaches, but if you have only two weeks I'd focus on London. But it is very very expensive. I'd come out of season to save money - you can halve your air fare to come in October over June to September for instance and you don't have so many tourists to battle through. You can easily spend two weeks in London and not have seen everything.
If you can hire a car then the National Trust homes all over England are beautiful, but these close for the winter at the end of October so bear that in mind. If you have particular interests in terms of members of royalty, sections of history then you can visit those that appeal most.
If I were coming here and had just two weeks and didnt have any family that I needed to see en route then I would probably spend a few nights in London, do the Millenium Wheel, dinner at the Langham Hilton (bear in mind last time I ate there it was just 3 people and it came to $600 but you have a view over Buckingham Palace and the food is pretty damn good, but its a bit formal). The Cinamon Club is a gourmet Indian restaurant set in an old library and a bit less pricey and serves the best house belinis, but you need to book these places - the waiting list is long. For a very fine burger and informal atmosphere try Giraffe (restaurant chain and you can eat here for under $20 per person and be well satsfied) on the Thames Embankment not far from the Tate Modern Gallery which is worth a visit if only to laugh at what passes at art and for the curiosity factor - plus it is FREE. British Museum - especially the Greek and Roman and Egyptian areas are awesome. And of course i'd say book a matinee show in the West End - i went to see Spamalot from the Monty Python team which was fun and you can get tickets to that for under $40 if you go for an early show and book in advance. Its slap bang in the middle of Picadilly Circus another famous landmark and of course Soho - the seedy sex area, which really isnt that seedy at all.
A Saturday afternoon at Covent Garden - look for the Cornish Pastie shop (they are worth a try too - very very filling and will only set you back a mere $6) is also fun. There are lots of boutiques and market stalls selling all kinds of curios and jewellery and hand made stuff to browse around. Above the Pastie shop is a tiny oak beamed bar which has a roof terrace from which you can enjoy a pint of cider and watch the street performers below.
If you have kids with you - take them to the National Science Museum - i think its still free and lots of fun and learning to be had there. if you are into war stuff - then the Imperial War Museum is also excellent as are the fairly new Churchill Cabinet War Rooms and Museum.
If its sunny - then a stroll around Hyde Park, which is huge and the Serpentine Gallery within the grounds is lovely.
Then after London I'd take a train to York, beautiful city - much smaller, cobbled streets, bags of history, much friendlier and personal than London.
And then continue on up to Edinburgh by train - but thats for another trip....
