Winter growing & Greenhouses

I've just put in for another plot of land next to mine (6m*9m), and I'm going to put a greenhouse or large polytunnel on it, hopefully this month.

As I'm a newcomer to fruit & veg growing in general, I have no idea which crops would be suitable to plant in it during the winter (if any), and if so, would I also need something like a parrafin heater (there's no electricity close).

I'm quite happy to put anything edible in there once it's up, and willing to give anything a try

last year i did have spuds growing over the winter along with lettuce, I would think about the costs thats incured if you use the parrafin heater would make the veg expensive