18greens
I agree that the IMCR does the UK adequately to get from A to B - unless you fly a deiced turbocharged piston or a turboprop. Or unless the top is well below say FL100 which is easily reachable by any decent SEP.
However almost anyone flying seriously is going to go abroad, and it then becomes plain very quickly indeed that an IR is needed to do planned flights. Just as the IMCR or IR is needed to do planned flights in the UK.
There is a weird issue with IFR outside the airways being permitted or not in France. There are differing views on it - I was told by a ATCO at LFBZ that it is not permitted. Others suggest that he was wrong.