Hi Puckymup, wow, that sounds like a great opportunity. I'm fairly new to the allotment game myself, and getting the amounts of things right, but ours is about 10x7m and you can pack a fair bit in. Also depends how many hours a week you think you are going to be able to spend on it in the growing season. As for what to grow, it depends when you are going to get started really, I'm still very much doing summer stuff only, most of which is either in or in the greenhouse waiting, not so sure about later in the year crops. That's the good thing about being on this thread, everyone says what they are doing so you pick up what to do when.
Well, managed an hour up at my plot this afternoon with DS, which was really nice. He's not interested in gardening , but was happy to gather a load of snails and make them run races along my bench box thing. He also enjoyed looking for baby slow worms, I reckon we've got at least three nests of them, I will say one thing for the using cardboard as mulch, it certainly encourages a lot of beasties to make homes under it.
My friend two plots down grows lots of runner beans, probably about 20 plants. She asked me to keep picking them while she was on holiday to keep them cropping and I reckon I filled a carrier bag each week with them, definitely too many! They do look stunning in full flower though.