Mk old type possibly would fit the ones with open terminals also some crabtree open terminal ones possibly would fit also. I don't tend to get many MEM mcb's infact can't ever remember taking one out whereas MK and Wylex have hundreds of all different sizes.
I have a DELTA [M9] 201C 'C' type 20A if it's any use to you ...well I have 2 actually but one has a 'chip on its shoulder, to the side of the toggle'... :coat
Thats good news and thank you for the feedback Sellers. Sometimes we never hear from a thread starter if the forum has helped to sort out a problem. Always good to see a matter is resolved.
They have an MEM board on the job I am doing at the moment needed a 32 amp to temporary power up the ring main again and had an NB Wylex 30 amp on the van they are a perfect fit. This may help somebody else out if they are short in the future. Mem stuff is a lot rarer than the Wylex NB stuff.