cyclocross bike
36/46 (110 pcd compact cranks) with a 13-26 10spd cassette
That said London is very flat so I only really need the lowest gears some of the time. I previously struggled with a 38x25 so it's a change but not by much as I avoid the really steep hill now.
The new cassette sounds like the best bet
or
change to wide ratio hub gears (rohloff speedhub is the best but it's initially expensive - low maintenance and general bombproof build makes up for that in the long run)
or
try and find a set of triple cranks with lower gearing than you currently have (you'll need to change the front derailleur and shifter)
http://www.rohloff.de/en/products/sp...son/index.html
