Tyres for Mk1 17" straights

[dave23572]

Looking for some advice here:-
Sorry if this has been covered before, but after reading some threads I thought it best to ask specific question:-

My (not lowered) Mk1 180 car is mainly road use but will be doing two or three trackdays per year.

Looking for a good value but good performing tyre choice.

What sizes are people running on Mk1 17" straights?
I was considering changing from the OE 205/45/17 to 215/40/17.
I read they're cheaper as it's a more common size, but also the lower profile may help steering response.

But:-
What about wheelarch rubbing?
Will they look "small" on a non lowered 180?
Will the ride be much worse?
Will non OE tyre sizes affect speedo accuracy?