Yer the 888 seems to be the best track tyre although if you use it as an every day tyre they dont last very long.
With my new brake kit i would have to find some cheap 18" replacement wheels with toyo tyres if i were to do the same.
Only problem with doing as you suggest is fitting 4 wheels in your car without getting the seats filthy to from and on the track.... If you put a blanket on the back seat or builders sheet, the tyres slide about on track as a focus st member found out - nutbar....
If you are brave or go with others then when you are on track you can leave the original tyres at the side of the track with them... surprisingly i know three people who have had wheels nicked at tracks in the UK whilst they were on track when they turned up on their own and left their original wheels at the side of the track...
...This is why most drive 888's to the track then change when they get home back to normal road use tyres before it rains...