New Greenhouse
 

Hi,
I've finally got my greenhouse up now.
As I'm relatively new to gardening, I have a stupid question:
Will this greenhouse be frost free if I do not have a heater in it? (from now on until summer, obviously not in the winter).
It's not glass, it's thick clear perspex on the front and like, corrugated plastic on the sides, top and rear. Norfolk greenhouses refer to it as Twin Wall.
Here's a link to it so you experts can take a look.

http://www.norfolk-greenhouses.co.uk...ef=86~0~SEARCH

I have seedlings (in cells), plug plants and begonia's I started from bulbs, to put in there.
I also have dahlia tubers to start in pots this weekend. Can these go in the GH, or should I start them indoors?
I do have a little parrafin heater, but would prefer not to use it yet (would prefer to wait until next Winter).

Thanks in advance

I'm in Essex.