I'm starting to think about outdoor runs too. I have a couple of those sectional metal runs that peg together (I think usually sold as puppy pens or x-pens) but I really dont feel comfortable using those outside. Mine dont have solid tops, they have mesh that you sort of peg over. I think they would leave pigs and rabbits very vunerable.
Before we moved house 2 1/2 years ago I used to have several folding wooden frame runs that were 6 foot by 3 foot. They were fab, you could take the tops off to get in and pick up/put down the animals and it all collapsed down to store in the garage. I paid £40 from my local pet shop and I used to feel quite confident about the guinea pig's safety in them, but nothing like that seems to exist anymore.
I dont know if its the fact that wood has shot up in price? I have seen a much smaller folding wooden run in Pets at Home for almost twice the price! And one in The Range that I was considering.
I do have one of those triangular runs with a hidey house at one end, mine is about 4 ft by 2 ft and was cheap in Home Bargains (it came flat packed) at £30. Its OK but I'm not wild about it