I'm assuming you have the Natural HIstory and Science museums in your list already which are a must really, and free... Other things to consider would be the London Eye (great views but bad vertigo folks may not like it), the Tate gallery, St Pauls, Tower of London (always tourist-clad, but ok if you can bear them) and a bit odd but on a Sunday the City area is very quiet and a stroll around the Bank tube area can be interesting.
The Tower of London tour is brilliant. Seeing the Crown jewels is amazing.
Me = green + envy. I really wanted to catch Billy but it's the wrong side of paydayOnly set times are needing to be at the hammersmith appollo for Billy connolly
In my personal opinion Tussauds is seriously expensive for what it is.
Is Buckingham Palace open this time of year? If its open then its worth a look (largely because its surprisingly tacky).
I'd agree about the London eye, definitely worth doing once. Also, a tour of St. Paul's and the British Museum are also good; but frankly I'd get a decent meal and a few pints and not worry about all the touristy crap.
dinner and beer can be had anywhere - why bother doing it in london specifically?