There are many things to do for free, try Googling 'London for Free', that should score you some things.

Of course, the real touristy stuff will cost - the London Eye, Madame Tussauds, Planetarium etc, but many of the quality museums - Natural History, Science, Victoria and Albert are either dontation or free and are good standbys when it's raining.

Parks are all free except for Kew Gardens, which will cost if there is an exhibition on.

The Doctor Who exhibition at Earls Court at the moment (it may be ending soon) is good for an hour and not very expensive, but it's all the modern stuff... very little of the old Doctors.

For good, reasonably priced food, try the Wetherspoons chain of pubs. They allow children in the bar if you're eating, serve real ales, and the food is plentiful. There's a great one in Whitehall (Lord Moon of Whitehall or something like that) which is within spitting distance of Trafalgar Square, National Portrait Gallery, St Martin in the Fields, staggering distance of Pariliament Square and Big Ben, slightly longer stagger down the Mall to Buck House and St James' Park.

Leicester Square does still have the ticket booths, but nothing is cheap these days. Many theatres still have the late cancellations and the Globe on the South Bank does £5 tickets if you don't mind standing in the rabble for the duration.

Good luck.

LTS