Well here's a strange thing, my MOC 12 back Palitoy Darth has the same score more across the back as your Han. It doesn't go through to the front but weird how there's two similar cut marks, maybe factory store purchases?
As for estimates -
12A Han with cracks in blister - 122 GBP November 2014 (yes that one was cheap and I think picked up by someone on here

)
12A Han not the best condition - 1009 GBP March 2014
12 Han card faded a bit - 1300 GBP March 2013
12 Ben not the best - 1000 GBP March 2013
Don't seem to have any other notes so Ben's don't come up that often although both of these may well have sold at auction recently which someone might know at what cost.
My estimate would be 1-1.4k for the Han (maybe less if the person interested wants to grade it) and I'm thinking 2.2-3k for the Ben.
There's this one that didn't sale which isn't in as good shape ( unless it sold outside of ebay) -
http://www.ebay.co.uk/itm/Palitoy-Star-Wars-12A-Back-Obi-Ben-Kenobi-MOC-Sealed-Original-UK-1977-/141562439736?pt=LH_DefaultDomain_3&hash=item20f5c76838&nma=true&si=N7xt4Ed1P7%252BhLptlmEEg2Ys47TM%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557
I also seem to remember someone trying to get 3.5k for one on ebay as a BIN a while back but it wasn't in the best shape and didn't budge so I'm thinking collectors have been waiting for the right one to come along.
Love to here others thoughts.
Ian