Looking for advice on where to get a whelping box. 48" x 48". Would prefer not to spend a fortune as only going to be used once every 3-4yrs. Are there any preferences on type/make? Where did you get yours from and at what price?

Because I only breed occasionally (usually 2 years in between litters, next time it will have been 4) for my large breed I simply buy wood, knock a box together cheaply and burn it after each litter. No germs hiding then and no storage problems.

Our neighbour is a carpenter and he made ours for the price of the wood (and a bottle of something). It will be used for fire lighters when finished with and a new one will be made if and when it is needed next time.
It has done the job perfectly (although the sides were a little low and the 4 week old pups are now on the move!)

I use a pool and sandpit case! Large apple sandpit comes in two halves, so one can be used whilst the other is being cleaned, inside a very large swimming pool (empty!) which is very easy to clean too. I line it with papers and puppy pads and then vet bed, and the same in the sandpit, so I can just remove the pit when the puppies start walking. Easy to store and easy to clean.

Weve made ours, 4 sides of treated mdf and painted gloss so its wipe clean. Hinged flap for door so mum can get out and puppies cant. Lino tacked to underside, flip it over tack it round the bottom and then flip back. Sealant stops poo getting in all crannies. Not attractive but fit for function.

I use puppy pen panels on a waterproof base (an off-cut of cushion vinyl 5 feet square or larger works well). 

Four panels and one on top (fixed with plenty of cable ties in case the bitch decides to climb on top when the clips might not hold) give rigidity and allow a blanket to be put over the top to make a den.

I line the inside of the pen with cardboard up to about 12 - 18 inches high (fixed with cable ties).

With this set up it is easy to extend adding more puppy panels to fit your space as pups grow (top removed of course).

The panels have a multitude of uses for pups, camping etc.

I now have a plastic one by Linkabord but not had use of it yet, before that I had a puppy pen with underbed storage box base at one end and once the pups got on the move swapped to a tray that is used for potting up plants that I got from B&Q for £6.99, with the lower front they could get out to toilet and back in again with no problem.

I got mine from Steel City, had it made to fit inside of a Croft Freedom pen, so could put a blanket over the top, nice and snug.