Hi
The problem I found was at the rear, with tyres catching the bulkhead area behind the door.
I have fitted 195/70's on 5.5 J rims OK, these are slightly lower than standard 185's. Being modern tyres the width of tread on the road is greatly increased and the handling is much sharper, they could have been made for the car.
There are many tyre size comparison checkers on the web, I use Toyo tyres myself. Perhaps 205 mm would be best on your 6J rims as long as the offset is not so much to make them catch on the bodywork.