XK8 tyre sourcing issue 245/50 ZR 17 99Y

[nick.metals.moore416]

Advice please. I have a 2001 Xk8 Convertible. Both rear tyres are worn and need changing. However, tyre specialists are struggling to find and source the size. The tyres are 245/50 ZR 17 99Y. The tyre shop suggested I replace the 17" alloy wheels with 18" front and back which would future proof the car being able to access the bigger range of 18" tyre makes. Downside is cost of new alloys and is there a market for my 17" alloys to offset the cost? Also should I keep the car as original as possible? Car is a weekender so not huge mileage but maybe it will become even more difficult to source replacement 17" tyres in the future as fewer and fewer manufacturers provide them. Thoughts?

[Lucky]

Give the Pirelli Performance Centre in Burton-on-Trent a call. They may have the original 17" tyres.