Thanks for the useful and thoughtful replies...
I tried sourcing Eagle F1s privately through mytyres.co.uk to no avail, so today I called Goodyear-Dunlop directly. After a lot of wrangling and and calling their tech guys (not much help) and calling the contact centre back again, I got a (sort of) date for production of Eagle F1s in 255 40 R17... December, or maybe January! They are producing enough to clear the back orders plus a few spares.
The tech dept. said Dunlop's SP9000 is standard on an Audi S6, but inferior to the Eagle F1. The SP8000 has frustratingly been discontinued - was Porsche approved for the 993 and was my second choice
Anyhow, I've placed a provisional order (no obligation, no deposit or anything). My work have an account with them, so the price is discounted to £75.52+VAT (so probably £100 per corner fitted). I know the Bridgestones are a great tyre, but they're a bit too pricey for me. The GSD3 is a direct competitor and I can't get anywhere close to £100 fitted with the Bridgestones.
If they don't turn up in December, I'll be thinking again, as by then it will be a question of legality! Can hold out until then, as since we moved closer to work, the 944 is basically a garage queen, so only used approx 40 miles per week, if that. Based on everything I've read / been told it'll probably be the Toyos if all goes pear shaped at Goodyear - wear rate not too much of a problem for me! Sadly they're not planning to ever introduce the all new Eagle F1 Asymmetric in 255 40R17 either. Boo!
Cheers,
George