Coincidentally I had the exact same fault only last week! lol...
(2002 Full Monty gen 1 with 50k miles on the clock, always garaged, but washed virtually after every use...)I initially had a problem with my lights shorting out and blowing a fuse. This worked out to be a spade connection that came lose from my front brake lever and was shorting out on my handle bars...
Anyhow, whilst searching for this short I also discovered the exact same burnt out electrical block cable as you Mike. So I popped down to Maplin and got a replacement 30Amp (Optimate type) connector and 30Amp cable. I must have been just around the corner of having a Total Electrical Failure myself!
All fixed now though + some WD40 action and a check of all the other electrical connections etc... There's another electrical block inside this rubber boot that replaced last year for the same thing! It's the white one with about 6 feeds running through it." Definitely worth checking out / replacing if not done already"