Is a conversion a lesser beast? (a long poorly focused ramble here)

You had bad luck with your snap thats all.

Do Archie Wilkinson Cycle Speedway frame have clearance for 700c wheels then. I am guessing even though speedway frames run 26" wheels the larger tyre means there is clearance enough for a 700?

Yup, ive had a talk to him. He has one built up in his shop with 700's, Ive been planning to go for a look but without a bike to ride there I have been putting it off!

they need a different fork though, as modern speedway forks are ZERO rake, so a there would not be clearance for a 700.