update:
Well, last night I picked her up from the MOT in Bath. I got as far as the services on the M4 before she decided to suck a load of carp through the fuel line and die. Consiquently spent a good 2 hours pi$$ing about with it using a head torch and a pen knife trying to sort it out. Eventually discovered at some point someone had fitted one of those in line fuel enhancer devices (whch do nothing BTW). This had broken downwith age and turned to sand, whch had been sucked into the carbs. waiting to get towed bak to bath to rip th carb off and clean it out. Wil try and get home later if it works....
Quite an introduction to classic motoring