Luddite, good vid, and your later Porsche description something I hope to avoid! I have it all back together, with a narrower new belt, on minimal tension. Thank you Richard, I have a (novice) track day booked for Thursday( BP to myself, pre booked a while ago, and non-refundable!!), so have decided, after consultation and much air sucking through teeth in the company of Mr Foxen, to risk it and delay workshop until next week. A shot of radweld (ughh) and a gallon of water for peace of mind, not to mention a wing and a prayer, will hopefully see me through the day- new (second-hand) radiator is holding water, and the fan is working as expected, so hope to avert any serious disasters!!
