With the new Octy due in the early new year at some point, at what point will Skoda stop taking orders on the current shape and what sort of discounts should customers be pushing for, realistically, if ordering new?

check out drivethedeal.com that is normally the barometer of what discount you could achieve from a dealer.

£17690 for a CR DSG, with a couple of extras (alcantara, rear parking). Although black alloys aren't listed on DTD.

Would GFV on a PCP be lowered with the new shape coming out?

I imagine they will still be selling the stock of the old shape new on the forecourts for a while after the new one comes out.

Depending on the supply and lead times on the new ones I suspect they'll chance their arm with quite high prices for new 'old' models.