Conundrum - How to get the best out of Strawberries in a PT?

Hi now I grow my strawberries in containers in the polytunnel then when they have finished fruiting I take them outside to make room for my tomatoes ,a good run of frosting does them the world of good who knows why but it does,mine are all in old 10 litre paint buckets 3 to a bucket 32 buckets and with all the runners I get loads of new plants every year ,I put a wee tad of fish blood and bone every spring and being so far north portglenone n ireland I get strawberries out of my 42 x 16 polytunnel I get strawberries six weeks before anyone else