Croqueteer
You have accepted the risk that if the clag is on the ground
Who mentioned flight when IMC is all the way to ground? That's a flight planning issue, which works against a single engine plane, but it's very rare.
can have heavy icing including freezing rain below 10000ft in the UK
Possible, in stratus cloud which is what I said, but not very likely?
Freezing rain occurs when snow falls through a warmer layer and melts.
No aircraft is certified for flight in freezing rain,
AFAIK.
The standard escape route for all icing conditions is a descent into warmer air below - another flight planning issue: make sure 0C is above the MSA. A good escape route from freezing rain would be an immediate 180.
You are automatically assuming that every pilot is an idiot.