Ok this is not rocket science.
You need to find an engineering shop that does line boring.
You then ask them to bore the hole in the slider true for the full depth
If the shop hads the gear to bore your legs then see if the same shop can turn you up some oversized bushes.
This is SOP for old fork legs.
If there is some one in the BSAOA on the list I am sure they have lists of shops that regularly do this work.
I got my B40 bored out by the local gunsmith ( how appropriate ) who also turned up the new bushes out of LG2.
So finally after several years of fetteling I had this bike all sorted & turned my attentions to the A 65 then some ******** stole it.