I had intended to contact KRK, but I wasn't 100% certain of the legitimacy of my mate's
ownership of the speakers

(I have
since been convinced), and that will be my next step.
I knew they wouldn't
sound the same, but at the moment I can only afford either replacement tweeters or a
sub-200 quid pair of speakers I reckoned that new tweeters in these would be the better
option.
Cheers for the help good sir, much appreciated.
--------------------
Mahalo