Well, the problem has been solved. A short occurred in the first Tortoise to be wired up, that connector strip I complained about above was the problem. Everything is wired back to where it was and I have had trains crossing the scissors in all three directions. The irony is that the short occurred exactly as the front bogies of the Jubilee crossed the insulated gap between oval and scissor crossing, leading me to assume that it was the crossing that had the short. An afternoon that was heading for disaster has been rescued by a brief evening's work. I have just seen Martyn's post (above) - I hope that with better wiring I can avoid the extra expenditure of the frog juicers. Five Tortoises wired now (only three levers though) with plenty more to do. I am going to pre-solder up the connectors where possible and improve the insulation to avoid shorts.