Weather reports suggest frost and snow this weekend.
What do I need to protect and how - fleece or polythene?
I have early spuds in along with onions, shallots and overwintered garlic and onions.
I would suggest that all those things will be fine except for the spuds which i would cover with fleece or newspaper if they are showing above the ground yet. i see you are isle of wight so i shouldnt think any frost would be too heavy there. famous last words.... ;D
This is a copy of what I put in the 'edible' section;
If the snow comes before the low temperatures this will give some protection.
Your potatoes should be OK providing the tops have not emerged and you have sown them quite deep, I doubt if we will get any penetrating perma frost now.
Regarding the onions you might have to check them all after the frosts to see that they have not heaved out of the soil.
Now you see why Tim and I have left ours still in the trays/bags ;)