lewis = oxford is very simple, looking at one worded clues we have:
continued - preston (pressed on)
leaver - exeter (exit er)
cleats - newcastle (rearrange cleats + new [word])
dagenham? - hereford (ford is here)
ern is - inverness (not sure about that one!)
so i think there must be more to lewis (loo/lou is..?)
I agree machel, it's a shame Bognor isn't a city.