This probably won't be useful to many people, if any; I had to replace the oil pressure on my N15 and went with an aftermarket one as it was dirt cheap. The socket required to fit the aftermarket one was a 24mm deep socket, however the genuine original one required a 26mm deep socket to remove it, or a 1" if you wanted to smash it on with a hammer. Hopefully this will help people in the future as I got caught out with only the 24mm socket and had to get creative.

Cheers.