Hi, Expert Sir Sparks here. I am a qualified USA Master & UK Electrician as well as many years world wide experience. I will do my best to help.n I will check to see if I can find the wiring diagram on line. You are correct that N will be neutral and L will be Live power in.
If you have tried it both ways it is possible the timer or themostat is now burned out.
Are you saying that when you tried my advice (both wiring ways) the boliler did not ignite? but the fuse did not blow?
Also where is the blowing fuse located?