Hiya Nick,
I'm an ex janner myself, have moved up to exeter now though (to be closer to civilisation). In your local area there's only one site; Mad Mommas Airsoft - they're in Trematon just past Saltash and do a game every few weeks. Only way to keep up with them is on Facebook:
https://www.facebook.com/airsmurf?fref=ts
It's a nice site for beginners and everyone there is very friendly, the rules are a bit unusual though, and quite often players get a bit of a culture shock when they go to a different site where people aren't wrapped up in cotton wool so much!
Venturing a bit further afield (and I would recommend it, Mad Mommas is good, but it's a very small site) you've got Skirmish Exeter (
https://www.facebook.com/groups/skirmishexeter/?fref=ts) which is a VERY large paintball place in stoke woods near Exeter, they run a game every 2 weeks on Sundays and generally have a much bigger turn out, as well as more involved games.
Going down into pointy head land you've got Cornwall Elite Airsoft (
http://www.cornwallseliteairsoft.co.uk/index.html) and KGB Airsoft (
http://www.kgbairsoft.com) - neither of which I have played at but I've got a few mates who've played both and their impression I get is that Cornwall Elite Airsoft is the one to go to.
Outside of those there's a few paintball places that do private/invite only games in and around exeter / newton abbot but generally you'll need someone to vouch for you as well as your own non-twotone gun to go to those.
Hope that's helped, any questions let me know