Have you tried your local pet shops? I tend to avoid those that sell animals, but some just sell supplies and hutches. I paid just under Â£90 for a double hutch for summer use. Well as I bought 2 just under Â£180 :
Delivery was Â£1.00.
Sometimes they be bought in the free ad papers, but I'm a bit leary as I worry about cross infection. But maybe I am just too fussy :-\
It might not be such a problem with runs for the garden?
As I said a good place to look for runs is in the free ad papers, I've seen them advertised there before. You could also place a wanted advert.
If you run a rescue, why not contact your local paper and and ask them to run a story about the rescue and an appeal for hutches and runs. I've done that before and received a good response. Mind publicity is a double edged sword as you may find you get quite a few calls asking you to take in unwanted guinea pigs as well as thier homes :
An Argos grid can be used for constructing indoor pens, have you seen the cavycages site, there are pics on there.
Do you want this for indoors or outdoors? For outside the happyhutch company sell 4ft hutches with 6ft by 4ft runs for Â£90 inc delivery - just keep bidding on ebay til you win one Not the best time of year to be buying outside hutches for piggies though.
For inside 48" dog crates from ebay are just over Â£40 delivered. You can house two pairs of piggies in one of these on two levels giving them a nice amount of space. The size is perfect for running in circles 8) With a stick bridge added for each group your piggies will love their homes. You can stack two crates and so house 4 sets of pigs well for Â£80 plus a bit for plywood to make the extra shelf in each.