I've seen some leaks that suggests the 5090 will be like €1200 more than the 5080, though it's based on the price of a full pre-built system and not all parts were visible on the leak (like maybe there was a different power supply), plus you have the cut for that business building the system.
So the true price is probably a bit less, and it's euros so it should be a bit less again in GBP.
My guess would be that the 5090 is more like €900-1000 more than the 5080 if you were buying it standalone, which if a 5080 is going to be £1200 that would put the 5090 at roughly £2000.
This wasn't the Nvidia reference edition either.
The 4080 didn't sell well at £1200 so maybe the 5080 will be cheaper than £1200, but stick around £1200 due to "inflation", and such.