Put mine up about a fortnight ago and I'm much further north on the east coast of Scotland. They're thriving so if I were you I'd just put them up and leave them.
We put ours out in the first week in June. We are at latitude 53 degs. 45 mins. north, and approximately 200 feet above sea level, which puts us in the wilds of Yorkshire.
mine are like youre maggie - in at night and out in the day( provided it's not heavy rain and/or very windy which can damage the young plants. probably leave them out all the time toward the end of May - we are in derbyshire
If you are worried about frost and cold over night. How about covering them with plastic bags at night and taking them off when it warms up in the morning
Mine must feel like yo-yo's! Never had to do this as often before- I have already lost four tubers to frost! Mind you-we are in Scotland.....yet oddly enough I have a climbing rose now on its fourth or fifth bloom which began on the last warm spell we had in March (I think) Very strange!