Star Wars cards, especially 12 backs, are very hard to price at the moment as they have been selling for crazy money recently (even recarded crap seems to sell!)
Ben
Ungraded 21 Back sold for less that £300 but looks in good shape - I would think an AFA80 would be in the region of £350-£450
http://www.ebay.co.uk/itm/Star-Wars-1977-Vintage-MOMC-Ben-Obi-Wan-Kenobi-/161070972568?pt=UK_Collectables_SciFi_fantasyCollectables_EH&hash=item258093fe98&nma=true&si=xQx8UWK%252B5tN99GUN0WAM%252B42cOkM%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557
A 20 back 85 sold for $600
http://www.ebay.com/itm/AFA-85-NM-20-Back-Ben-Obi-Wan-Kenobi-C85-B85-F85-CLEAR-WHITE-HAIR-/360716647774?pt=US_Action_Figures&hash=item53fc633d5e
Jawa
A 20 back AFA85 sold for $651 last month so I would say £350-£450 would be on the mark for that one
http://www.ebay.com/itm/STAR-WARS-JAWA-20-BACK-A-AFA-85-/190875484422?pt=US_Action_Figures&hash=item2c7110c106&nma=true&si=xQx8UWK%252B5tN99GUN0WAM%252B42cOkM%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557
C3P0
A 12 back AFA85 sold for around the £500 mark and an AFA80 for £440 so I would say yours is worth around the £400-£500 mark
http://www.ebay.co.uk/itm/VINTAGE-STAR-WARS-KENNER-12-BACK-C-C-3PO-AFA-85-80-85-85-MOC-/130970527898?pt=UK_ToysGames_ActionFigures_ActionFigures_JN&hash=item1e7e73a89a&nma=true&si=xQx8UWK%252B5tN99GUN0WAM%252B42cOkM%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557
http://www.ebay.com/itm/STAR-WARS-AFA-80-C-3PO-12-BACK-C-VINTAGE-MOC-/330991530898?pt=US_Action_Figures&hash=item4d10a1f392&nma=true&si=xQx8UWK%252B5tN99GUN0WAM%252B42cOkM%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557
Finally, Chewie
I wouldn't worry about the frosting (mould) this will come out with a few hours in the sun. Pricewise. I would say this a tough one - graded examples have been selling for over £1000 recently and even a AFA70 went of over £400
http://www.ebay.co.uk/itm/Vintage-Star-Wars-12-back-Chewbacca-AFA70-/290933696395?pt=UK_Collectables_SciFi_fantasyCollectables_EH&hash=item43bcffe78b&nma=true&si=xQx8UWK%252B5tN99GUN0WAM%252B42cOkM%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557
and amazingly a recard sold for £220
http://www.ebay.co.uk/itm/Vintage-Star-Wars-12-back-Chewbacca-AFA70-/290933696395?pt=UK_Collectables_SciFi_fantasyCollectables_EH&hash=item43bcffe78b&nma=true&si=xQx8UWK%252B5tN99GUN0WAM%252B42cOkM%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557
I would say that yours could be worth at least £400 and probably closer to £600