Peter
regarding your plus 4 you should need a 195/65/15 to achieve a comparable height. I only have found winter tyres of this dimension.
If you have 6.5J rims why not to try 205/65/15?
205s would be wider than the mudguards. Michelin, Toyo, and Bridgestone all make pretty good 195/65 R15 summer tyres in H or V rating. The only thing is they have a slightly higher load rating at 91.