A while back I wrote a couple of blog posts about getting online while camping ( On t'Internet in a tent and Surfing and turfing - Getting online while on camp ) In them I outlined the options from a purely theoretical point of view. Well as I've just taken delivery of a swanky new 3G phone (a Nokia 6220 with integrated GPS, as you ask) I thought I'd write an updated post, covering what I've discovered in the meantime.
Well the most interesting thing was how little of the UK has 3G coverage. If you move away from the large urban areas then coverage seems to drop off quite rapidly. OFCOM has published a pdf (here) showing the coverage of all the network providers and unsurprisingly 3 has the best coverage overall (I hope so as it's who I've gone with for my new phone). However after chatting on the camping forum it seems that in some areas other providers have better coverage. The Peak District is apparently well covered by O2 for example. So it seems despite all the hype 3G is still going to be problematic especially in rural areas - in fact precisely the kind of places where you find campsites.
We've not managed to find a site with WiFi yet and most don't mention whether they offer WiFi or not which is a little frustrating. It's now quite common however for pubs, cafes and restaurants to offer free WiFi these days, for example Wetherspoons, Little Chef and Costa Coffee. There is a WiFi hotspot finder here which seems quite good.
So all in all it seems that being able to surf the web while camping involves some forward planning to find a convenient WiFi hotspot or getting lucky with a 3G connection.
In the near future I think it's more likely that there will be an increase in the number WiFi hotspots rather than an expansion of the 3G network. But what do I know, I've only just got a phone with a camera.