aww, what rotten luck vickylou.
you can plant salad crops - lettuce, herbs, radish, carrots etc.
Japanese onions (these can be planted August-ish, to over-winter) ready for next spring.
Ditto spring cabbage
?try potatoes, you might get away with them before blight starts
to be honest, try whatever seeds you've got, while they're fresh. things'll grow well in a polytunnel