If you can't see at circling minima, you do not execute the approach, end of.
"end of." for your operation in nice, easy Europe
Showing your inexperience a bit there.
Other countries have different rules, and Cat C airports can have different rule-sets again. As stated above - in Australia, if you are visual at the circling MDA, you may then descend
visually to as low as 400 feet obstacle clearance in order to ensure that you remain visual. I have circled airports 400 feet AGL (200 feet below MDA) in B737 and BAe146 airline passenger operations in high winds and heavy rain several times in Australia.
At the old Kai Tak in Hong Kong, aircraft could not fly a straight final from anything higher than about 250 feet - that was another airport where a constantly turning final approach was
necessary.