What are we all using to keep warm co-sleeping? (UK)

I’m starting to get really cold co-sleeping now. The weather has gotten chillier and my hormones are making me freeze (15 weeks post partum I started my period despite exclusively breast feeding!) I have seen some good looking sacks on slumbersacks, but it’s just so out of my budget, especially as I would have to get a couple.

Last night I wore two pairs of trousers, 2 tops and big fleece!!

Any good recommendations/ideas out there?

Thank you