Seconded: Good for you!
A few thoughts:-
1. Do you have a driving licence? Ironically, almost every "environmental" job I see advertised requires one ( I don't - which is why I'm stuck in front of a computer and not out there doing something constructive).
2. Get qualifications - it's a very competitive world, and the better your qualifications, the better your chances of getting the perfect job.
3. As a starting point, try the British Trust for Conservation Volunteers - they organise volunteer work parties, and training courses up to NVQ 3 level:
http://www2.btcv.org.uk/display/btcv_home
For jobs try here:
http://www.environmentjobs.co.uk/
Good luck
Tursiops