Before you commit yourself to chopping the connectors off, check to see if there is any corrosion on them. A good clean with some sand paper on the male and female connectors may help. Also take the fuse holder apart and clean up the contacts inside. Plus clean the fuse ends. My Optimate, like yours, would sometimes charge if I wiggled the fly lead. Since cleaning all the contacts it has worked perfectly. Must be down to having such a damp year again. If you do need to replace the male/female connectors then Maplins do them. I converted another charger I had to work with the Optimate flylead. From memory the black and red leads on the Maplin connectors are opposite to the + and - leads for the Optimate.
http://www.maplin.co.uk/Module.aspx?...I D=3&doy=3m1 Hope this helps.