I love the idea but I'm not sure the answers are totally right...
+ Several of these places aren't cities
+ Urmston, as a suburb of Manchester, isn't much more than half the size of Uxbridge, a suburb of London. I suspect the largest town in its own right beginning with U is Uttoxeter
+ The largest place beginning with K I think is probably Kingston upon Hull, at 269k. (It also has the merit of being a city!) If you think it begins with H, but you're allowing suburbs, then Kingston upon Thames is also larger than Kettering
+ Several of these places aren't cities
+ Urmston, as a suburb of Manchester, isn't much more than half the size of Uxbridge, a suburb of London. I suspect the largest town in its own right beginning with U is Uttoxeter
+ The largest place beginning with K I think is probably Kingston upon Hull, at 269k. (It also has the merit of being a city!) If you think it begins with H, but you're allowing suburbs, then Kingston upon Thames is also larger than Kettering
Sorry to nit-pick. I did enjoy it!