Some random thoughts:

165s on 6" wheels are outside most manufacturers' recommendations, but will work without issue (other than making the rims a little more vulnerable to kerbing).

T-rated tires aren’t a problem on a Fulvia, being rated for continuous speed of 190km/h (118mph).

For road use, it’s almost always a better idea to start with the factory spec, wherever possible. In most cases, any additional lateral grip from wider lower-profile/taller tires is offset by losses on steering precision or changes in effective gearing.