Thanks for all the advice, I am very grateful. It turned out the low tension connections to the coil were badly corroded, I took out the coil and cleaned all the terminals. Once they were cleaned it fired up straight away. I am gonna clean up all the connections as most of them were corroded to some extent, 31000 miles in all weathers has taken its toll.

I have a couple of fault codes to clear but I think they are from when I pulled connections with the ignition on.