Nokia is available on Play.com but for £100 doesn't offer that much…
Another option would be a Sony Ericsson C702, it`s dust and waterproof, has GPS and good camera. Unfortunately the case quality is pretty poor as it wears out quick and the phone although still working fine looks tatty. My friend has one and uses the mapping function when on the bike as he can always check where he is if he's lost. But it has aGPS and not GPS and that's probably not the same thing and if You don't have a signal on your mobile it will not show you your position.
But again touchscreen phones are in fashion now, so getting a classic looking handset might not be a good choice 🙂 Genio is the newest one from the bunch, well priced and quite heavily advertised now as well 🙂