Thanks Waz. I should have mentioned I had the humbucker sorted, and yes, you picked the right screws, but thanks to the photo being so blurry, you can't tell that they are in fact brand new screws. They look like crap because I checked them in the humbucker tabs to ensure they fit, and one side is perfect, the other jams up and has stripped the threads on the screws, luckily I have a couple more, but I may have to re-tap the dodgy side. The guys in the workshop may have something that I can use.
As for the single cavities, there is not enough room to slide the springs down the side, and because I have undercut the side of the cavities to take the single Pups I got off you, it is a really tight squeeze. The original pups were screwed into the timber, so there are already some holes in place, and they match the replacements. I think I will try a dab of superglue to hold the springs in place.
As for the foam suggestion, where would you suggest getting some from?