Thanks for the suggestion Wayne but the killer with these deals from the States is the hideously overblown postage cost. In this instance eight quid for the connectors and fourteen for the post - on a pack that will weigh less than 100 grams even with all the customs labels pasted on.
I’ve also found the average American is appalled when I suggest that the package be labelled as a gift. If even a penny of customs duty needs paying the parcel carrier acts as the agent for HMRC and collects the duty - plus an eight quid fee for doing so.
I’m away to check which of my batteries fit the long but slim battery cutout and will modify connectors to suit