PSB will be ready much earlier and bring your cropping period forward, all kales likewise, any overwintering cabbages, spring cabbage, any other brassicas you can think of relish the protection from wind and rain and pests!
Mustard greens, perpetual spinach, chard, winter radishes (try the blue and red ones called Blue Moon etc from T&M, they are amazing!) , Spring Onions, shallots, Autumn sown bulbing onions (Japanese onions) multi-sown in modules then planted out in there. Whatever hardy salads you like, early sowings of carrots and beetroot, plus new potatoes from, mid February onwards, especially if you can give them additional cloche protection inside the tunnel, with peas, mangetout, Cherry Belle radishes, that need no extra help in there; broad beans (de Monica) from a Spring Sowing are incredibly early,
Just keep an eye out for whitefly on brassicas or aphids on peas etc... they also relish the protection and need to be dealt with promptly of they overtake everything at an amazing pace . No carrot fly, onion fly.pigeons or other flying pests. Mice can move in... snappy traps deal with these readily.
I wouldn't be without my tunnels in the Winter, and mine are not quite the area you have Simon (2 that are 6m by 3m which in Summer I join with a 1m wide netting section to give a cntinuois space but close them off in Winter to 2 spearate ones as they are warmer then.. moving in some tubs of mint is good too if you have space