Well All those prices I quoted above at CEX 5 days ago have all dropped by £2-4 pounds. Except HULKBUSTER, now UP to £15 ( £10 trade-in ). So CEX at least are citing HULKBUSTER as the current rarest / most valuable figure. Seconded by Judy Hopps and Spiderman.
And on another note - I bought 5 power discs from CEX online last week. They all arrived, but 3 of the 5 where wrong! They didn't check it at all, it looks like they just thought 'oh that looks like it'. They were from different stores too, so not just one staff error but 3. - Well they sent me one replacement, but told me to go in store and get a refund on the other 2. It's just a pain.