You could only get a static IP with Sky, at least with FTTC, if you had the Sky Fibre Unlimited Pro package. I do not believe you can order it anymore.
I have a single static IP with them through having that package, had it 6.5 years now!
Your other option is a "prosumer" ISP like AAISP, but they'll blow your budget. I don't know what cheap ISP's offer static IP's, I'm afraid.