Thanks for your comments
joseph woosey - your allotments sound wonderful
GardenNovice - happymarion's advice is always spot on. There should be no need to supplement birds' food if you grow enough berrying and seed-bearing plants for them. Grow plants like verbena bonariensis, agastache, teasels, sunflowers, cornflowers, honeysuckle, holly, guelder rose and dog rose. They will provide bees and butterflies with nectar and pollen in summer, then if you leave them throughout winter, they will provide much-needed food for the birds.
sarah's pondlife - I don't know about looking for a hibernation site, as frogs are cold blooded so they don't need to be warm, just frost-free. I occasionally get frogs coming into the house (if it's jumping, it's a frog). I just scoop them up and pop them outside again. It's probably the same one. Sometimes I think they're just having a look around...