I do of course fear that I will end up having to change the crank sensor but whether or not it flies in the face of all logic, my changing the thermostat does seem to have worked. Sometimes the empirical is better than the theoretical. Time will tell.
UPDATE
Well, it's now been over three months since I wrote the above... ...and, at the risk of "speaking too soon", I'm delighted to report that changing the thermostat really does seem to have entirely cured my hot start problem. I've just just completed a touristic rally in Alsace (NE France) starting from the Charente (start of SW France) and completed nearly 2500 kms in 8 days with loads and loads of hot starts and did not have the slightest problem restarting. For those that are thinking that my thermostat being slow to open couldn't possibly cause a problem restarting, my thoughts are that whilst in itself that may be true, the slow warm up was throwing up a fault code (P0128, and the ONLY code I was getting) and that perhaps it's the presence of this fault code that upsets the fuel mixture, causing the difficult hot starts I had been (should I really have said that?) suffering from.
I'd removed all the engine bay trim in order to gain better access to replace the thermostat, and I have decided, however, not to tempt fate by reinstalling all the trim until several more months have gone by.