Omlet/Eglu do look nice (insulated so warm in winter, cool in summer) but even on Gumtree they are £250+.
And small.
There's a rabbit hutch I saw online called "BunnyBunker" which though it's £400+ (ouch) looks better value in view of space but it would need adapted to let piggies climb to the sleeping area.
Steviebuns are you planning keeping your hogs inside or outside or both?
Inside you can keep a closer check but you do need a big enough cage and a run (C&C are good , you can adapt it to suit yourself and make two levels, but a lot of piggies don't climb well)
You'd need MINIMUM 2'x4' for 2 adults but bigger is better.
The hay gets everywhere, I kid you not 
Outside you need to protect them from heat,cold,damp,wind,predators.
The two level hutches that you see have a very small sleeping area and are usually shallow so the open meshed area can get wet (you can get waterproof thermal covers for them). The bottom layer can go on grass but it would get churned up quickly and they're heavy to move.
Hay- it varies. Some is dusty (not good) some is coarse (also not good) I only buy Small Animal hay and soft barley straw to bulk out a winter bedding.
I do buy equine cardboard shreddings for the floor (huge compressed bags of it).
Equine hay/straw is too coarse for rodents.
Mine live in an old wooden Playhouse - you could consider a shed but make sure it's ventilated,secure and won;t get flooded.
My DH has made a load of our pigs accomodation. At the moment they have a three box run made from an old bookcase with doors cut to each section. And a big haybox made from one of those plastic lidded garden trunks (for garden cushions etc) with two doors cut.
DH was delighted when I showed him plans I drew for two colder weather sleeping areas I want him to build. I'm Gemini, I come up with ideas, I don't do them 
Bunny Business is good for outdoor runs (they can fold flat for storage)
Gumtree etc is a good place to search but make sure you sterilise 2nd hand (steam gun and white vinegar to neutralise the smell of other animals)
Make sure no-one has hay or fur allergies.
And guinea-pigs are addictive and collectable 