VERY nice seat bscrive!
I'm having my Corbin seats redone now by a guy here in DFW (thanks to WDAN for the referral) - Driver, passenger and both back rests, and since the Corbins were "broken in" by the P.O's (who I think were substantially larger than my better half and myself), I'm having gel pads pocketed into the OEM foam and covered by thin layer of foam. Hoping for a slight adjustment to seating position, and a little softer seat (but not the butt-numbing softness of the Honda OEM seats).
My upholstery guy is also using marine grade vinyl to recover. I've not asked for any decorative stitching.
He explained that the marine grade vinyl will stand up to the Texas heat/cold/wet/dry cycles better, be less "slippery" than leather, and not get as hot as leather does. Told me it's something in the chemistry of the marine vinyl. He said that he'd only recommend leather for bikes in the North, that only come out in the lovely, mild summers

Old2soon - WRT your question on costs in the US.
Material costs: the two gel pads and extra foam covering were $65 each, and the vinyl about $130.
Labor is going to run $300-$400.
I can tell you that I asked around, and got answers from "I won't touch a Corbin seat" to "$800 to recover in standard vinyl", so I was very pleased to find the guy who's doing the padding and reupholstering, as I didn't want to send them back to Corbin and pay 75% the cost of a new seat just to have them recovered.
Of course final judgement is reserved until we've gotten them back and done a long ride on them, but I'm excitedly optimistic, based on the recommendation and my interaction with the upholsterer to date.