Do I need a heated greenhouse?

I will be sowing some cabbage and cauli seeds shortly to plant out mid june.Do I need to heat the greenhouse?

 

You shouldn't need heat Neil , though if there is a chance of severe frost at the early seedling stage, some form of covering (bubble wrap or even newspaper)at night would be a worthwhile precaution.
Our cauli and cabbage were sown in a heated propagator in the heated half of our greenhouse last Sunday. When I prick them out into pots they'll go into the unheated, though well insulated, side of the greenhouse.

 

Thanks for the advice Dave W.Much appriciated.