Fellas! The new fuel pump arrived today in the early morning. I swapped it in and.... success!

The ampage reading is now a steady 3.6A, a little higher than I believe it should be but, there's no more fluctuations from throttle, stumbling, high amp jumps etc. The only thing left to do is ride off into the sunset,
after it finally stops raining.....
Regarding your new fuel pump purchase, if you've performed the tests correctly as prescribed by rbm and caveman. and described their results correctly, congratulations! You've bought yourself a spare fuel pump.
Spare pump? I think not.

Thank you all for your contributions to my problem. Glad we've been able to get to the bottom of this.
Seb