Guys, thank you all for the info and advice!
I went ahead with the purchase on PCP - the current deal is indeed 3.9% which is great in comparison to the rest of the car market.
First impressions - GS F is an absolute joy to drive, what a fantastic piece of engineering! The only downside is that mine does not come with ML sound although the stock Pioneer system is OK. I did some more research and the price of around mid to late 30K mark has been there for the past 2 odd years so it seems to keep the value pretty well. Given there aren't many about I think it will retain its value for another couple of years or even longer if the mileage is low and it has been well looked after.
I hope I have not been ripped off by the dealer and signed up to a very overpriced deal 🙂