Try Swiss Chard. It's pretty, delicious, nutritious, versatile, doesn't need a lot of space, grows quickly.

Salad leaves, spring cabbage, spring onions, radishes, beetroot, cucumbers, squashes - it really depends on how big your polytunnel is.

Thanks I have cucumber potatoes lettuce straws, courgette, French beans runner beans and the tunnel is weft by 16ft beetroot seedlings are nearly ready for thinning and I have planted spinach seeds and common the cob seeds

Sounds like you have it under control Tercol though not sure what 'weft' is :)

Sorry moongrower but my keypad sometimes stick or keeps repeating letters the weft was typed as 16 ft

Unusual to have a completely square polytunnel but it obviously works for you :)