Posted: 14/09/2014 at 14:53
Firstly welcome, you've come to one of the best places for free help I have ever known.
So far you seem to be doing all the right things so carry on what your'e doing.
As for the perennials, if they're as small as you say then I would leave them overwinter in the polytunnel for winter. they need a good root structure to thrive and I would guess they still have a way to go before getting there. When the roots fill the pot they'll be ready to plant out, and over the next month they should get somewhere near that point before going dormant in the winter. By that time the ground will have cooled significantly and so putting them then would increase the likelihood of losing them. When the days start to lengthen in April next year, as long as the ground isn't frozen then you can consider planting them out, so keep an eye on the weather.
Planting out in spring can be hazardous as unexpected cold snaps can do untold damage to newly planted out perennials, so look for a longer warm spell next year, even a few weeks of warm sunshine can give them a better start.
When it gets to that time, don't be afraid to ask for help on here, the only stupid question is the one that isn't asked.
Right now I would improve the soil in which you intend to plant them, will some well rotted manure. This will rot down over winter and give them a good start when they do go out.
Best of luck.