Any clues what this is? I'm out of ideas!

So I’ve been scouring image libraries of cacti and succulents and have drawn a total blank.

I bought this on a plant shopping spree around 9 months ago and have really struggled to care for it because I just have no idea what it needs! The label it had in-store was a different plant and the pot itself had no sticker. The website for the shop was no help either.

It was looking much sadder than this but have handed him over to my much more green-fingered mum to save him while we try to identify what he is!

Any help gratefully appreciated, it’s annoying beyond all belief that google-fu is failing me on this one.

Update: Solved, I think - Euphorbia Lactea Cristata of some sort!