Thanks for the input gents, I'm sure that there exists some corrison at that particular fuse carrier and i thought I'd got it cleaned up and indeed it had performed ok until as mentioned i switched on all loads, lights, blower, screen, and of course fuel pump.
One of the issues is that Omnitec manufactured "Morgan Dash Control Module", i think its supplied from the same fuse and i think that whilst i was installing an indicator buzzer i accidentally disconnected a wire from it and it also killed everything as i remember....but hey im starting ramble here. That panel i would like a little more info on, its a bit of a mystery and has i believe caused issues for people on here. I did manage to wire my driving lights thro' a spare volt free switch/relay on the panel.
Regarding the suspect fuse csrrier, i think a change out maybe in order which of course means the full 8-way carrier needs to be changed, its a dash drop job. I may choose to just install another carrier and connect the one circuit to it rather than change out all 8 circuits onto a new carrier unless they are spade terminals which would allow for easy changout.
Richard, yes the I^2R heat generated would of course melt the fuse assembly without blowing the fuse, I'd considered this but started to wander of into the hinterlands and vagaries of the Morgan wiring. I guess you've pulled me back on course here. I'd still like to know how much current is pulled via that one fuse.