The C.perforata was about this tall when I had it,right now it is in a very sunny porch so getting plenty of light.It may not have had good light while it was growing elsewhere!
The C.arborescens could be a C.atropurpurea possibly var.watermeyer?

Thank you for that,nice to know I can identify them OK.
I do need to repot them both as they are still in their original pots,job for tomorrow methinks!
Would cutting back the C.perforata be OK to do at the same time,at present it's just getting taller?

I bought these 2 plants and they were helpfully named 'Crassula'.I think they are Crassula arborescens and perforata.Have I got that right or does anyone else have suggestions!!