Farm work is good, but you do really need large animal vets as well. I know its tough, i live in the city and i think there is one practice anywhere near me so i wrote to them and they were filled up for the entire year and i was told to get back to them on the 1st of january of the next year! I know other people on this site have stayed in B&B's, or maybe arrange some vet work then try and organise a family holiday around it? I know both those options cost money and kinda need parental help if ur still at school...but there doesnt really seem to be much option. Also, if you've done farm work, surely those farms have vets? ask them?
Hope this helps x