Hi Julia,
you could register as a model RAM (Register of Artists Models) but this does cost a bit of money. As others have said contact local colleges of Further Education and Universities. Use search engines, Google, or whatever and think of all the local towns and villages and do a Search for Life Drawing and the Village town name. In my experience it took a long time to build up a few places where I model, also there are more male models usually than female, so you may be luckier. As for poses, usually allowed a break from the pose after 20mins or so for longer poses. Good Luck !