Thanks Wristpin, very useful, the basic carb body is the same, the mark 2 seems to have the little red plastic filter instead of the the plastic see through one.
I am guessing the red ones are hard to obtain? ....I am thinking that 3D printing could help with making them available again
I will have the carb off for cleaning tomorrow and now know what the innards look like!
I have discovered that my Mayfield has come home, it was built just 1 1/2 miles from my house in Dorking