Many thanks to all for the replies and information.
From another source I've been advised that Mod. 1530 deleted the switch and this was applicable to all S2b and S2c. At some point a technical instruction was issued to wire lock the guard on the button to prevent its use. Hence most RAF pilots/ground crew might be unaware of it, maybe except those flying S2a's with a pair of side cutters.
I've also looked through quite a few videos and pictures of cat launches and so far have only found one which shows a rapid undercarriage retraction so I guess, as correctly stated above it was only used occasionally. What combination of hot, heavy and low wind over the deck was it intended for?