Perhaps an Astrophytum? I hope I'm pointing you in the right direction. I don't have this plant, but I like it.

I was going to say exactly the same thing...

Oh absolutly! Thank you both very much

You called it a succulent which isn't incorrect but you can call this one a cactus. I understand it might not look like a cactus because of the lack of spines but it is a cactus. It is certainly an Astrophytum and probably the species myriostigma. Its common name is bishop's cap.

I agree with Polyponpholyx... A. myriostigma. Two of the three in that pot are A. myriostigma quadricostatum (the two with four lobes).