Hi Viks, I clean all mine with Jeyes when it is empty and wrap with bubblewrap, I see this lot have it on sale at the mo, bought some netting off them earlier in the year and they were very efficient!
http://www.lbsgardendirect.co.uk/default.aspDon't know how cheap it is compared to other places though cos I haven't bought any in years!
Over winter I grow mainly lettuces and salad greens, Mizuna, pak choi that sort of thing. Mine is so small that apart from one bed the rest is taken up with overwintering me tenders!
I have found that here in Sussex, I haven't had to have a heater, but would love to get leccie to my greenhouse, that would be a real treat! ;D