I often transfer bulbs from pots to the ground. It doesn't matter when you do it as long as you don't disturb the roots. I just tip them out of the pot and drop it into a hole I've just dug.

Actually a really good time to plant Tulips and as long as the soil is not actually frozen solid (which would make planting hard in any case), all the normal spring bulbs would do well.
I have often grown spring bulbs in pots, mainly because it is hard to know where the gaps are before the ones in the soil show their noses. They got planted out once the soil was beginning to warm up in spring, so when they were growing but not flowering. Actually it does not matter, if the winter persists, then the potted bulbs can wait until the conditions are right. The Tete a Tete daffs which get sold off after flowering round here get planted really late on and they have thrived.

I agree they can be transplanted any time, as long as the ground is not frozen. I have also popped the pot into the ground and then planted them out in a different spot later on.

Thanks for the suggestions. Think I'll plant the tulips now ( weather permitting), and pot up tete tete, muscari and another I've forgotten.
Best wishes. Thecat.