Hi- yes we had 3c last night and frost. I brought the pigs in for night time on Saturday (because of the fireworks) I'm hoping next week they can stay out in their Pighouse if it's warm enough. We'll see.
Hay- it varies alot. I think if you want green hay you need to look at fresh bales but you need to make sure it's dry (equines will use a bale of hay before it gets a chance to go mouldy ),
Hay has been rough the past couple of years because of the rain, I think this years is better. If I go to Jolleys, their own brand hay is lovely. And 'Readi-Grass' very green but dry, malty smelling. Not a hay substitute, it isn't as bouncy and it's a bit sharp.
The SnugglePads are hot when you microwave them (as in you can hold it, so not as hot as a hot water bottle) We wrap in newspaper and put it under their hay. It'll stay hot/warm for 8-10 hours. The pigs will sit on it, even without the fleece (which I got fed up with washing, my original boars were very productive )
Our small bedroom has no door and we keep the radiator off so they don't get hot.
When they go out, I have a mini-oil filled radiator that I put on 30 minutes before they do (I need to plug it into a timer soon, to save me wandering down the garden at 6.30am)
They have fresh hay and paper every day in their haybox ( I don't want to risk them on damp hay. It does flatten , and with three of them they do pee loads) When I had the GP1& GP2 pigs, they could make a haybed last longer just with picking out. (They are all different characters and habits)
You could get a tarpaulin to go over the hutch (leave ventilation space) easy to get hold off and much cheaper.
I've tried loads of things with our pigs over the time we've had them. They seem to like hay,cardboard boxes and newspaper.
I've changed my mind about fleeces, they don't sleep on them.
As long as you give them protection from damp, wind,predators, extremes of temperature and changes of temperature, they will snuggle in the hay and be toasty.