Thankyou for your replies folks, I should have put it was a euro. spec. swingaxle car with earlier pre-66 short axles fitted.

Here's a few pics., don't want to go to adjustable springplates if at all possible (asked as they were suggested to me as a solution rather than changing tyres).
Before (best one I have)

After

I want to keep the rear at stock height, would like something a bit taller to fill the arch a little better- don't mind going a bit wider on width, but nothing taller than a 65 profile.

Hope the pictures aren't too big...

Martin.