Not sure if it might be too difficult, but print out a blank map of London and they have to fill in some names. Go for the more obvious ones such as Richmond or Kingston, Croydon, Enfield, Westminster and their own school area. Or have the names of the areas as anagrams, (you could do this with tube names too).
Name as many museums and art galleries as you can.
Pictures of kings and queens of England to be identified.
What are the following places famous for? The Royal Mint, Billingsgate Market, Speakers' Corner, 221 Baker Street, 11 Downing Street etc.
Hope this is of some help.