Further to my previous post, I have recently come across a couple of quotes which you might find interesting.
In his book ‘Hedgehogs’, Pat Morris says:
‘In the warmer climate of New Zealand, hibernation is necessary for only a brief few weeks in midwinter, whereas in Scandinavia the winters are longer and so hibernation is prolonged.’
also re. Weights needed for hibernation:
‘The study in Denmark … suggested that about 510 grams is the minimum weight needed for survival, but Danish winters may last a bit longer than British ones.’
I’m not sure how the weather in Denmark compares with that in Sweden, but it may give you a better idea.