I wonder what the time difference was between loss of comms in the uk and his location in Switzerland?

Therein lies the mystery.

As he was flying Cambridge to Lydd he would not have filed a flightplan.

For a UK VFR flight it is very unlikely that any radar service would be tracking him. Certainly were I flying that route I’d sign off from Cambridge and would be unlikely to call anybody until passing Southend. Once clear of them no requirement to talk to anybody until 10 miles (or whatever) from Lydd.

That being the case, who called out SAR?

Moggy