Good news, the splitter arrived and it's deep enough to get to the pin and one of the pushers (can't think of the word) is the right size to fit in the hole.
Bad news, it's not budged the pin yet. Admittedly I didn't have much time to try it over the weekend but will try again when I can get another pair of hands to help.
I'm quietly confident.
P.S. It's the splitter kit in the red case from the popular auction site, about 9 quid