I've never used the preformed ponds - much harder to get right. I'm not sure what 'wool packaging' is like, but you basically need something that will hold the pond well, and won't shrink and cause instability. There are lots of threads about making ponds on the forum though. Most people prefer a liner, simply because it's far easier to do.
I use Bradshaws or Pondkeeper for liners. Both are usually very competitive. GCs will alwasys be expensive.I usually just go for the poly ones with a 25 yr guarantee. You often get holes from wildlife going in and out, so that's why I've never bothered with butyl.