I'm not sure which one of you wonderful people suggested this idea or in which thread, so sorry about that, but I'd just like to send whoever you are a big Thank You... It worked perfectly and I'm now a very happy bunny.
The suggestion was to put the cut batting down first onto the carpet (it stays exactly where it should) and lay the backing onto it right side up. fold back one half and spray, then lay out the fabric... smoothing out any wrinkles as you go. Then do the other half.
Turn the whole thing over and do the same with the patchworked front/top.
Usually, however careful I have pinned and basted, I have had the odd annoying ruckle or fold on the back once I've started quilting. But using this method, I had my smooth, sandwiched quilt ready to sew in about half an hour.
Thank you for a ruckle-free, no pain quilt session. This is going to be the way I do my quilts from now on. :thumbup: