Martin Whybrow wrote:

Chris
I have a cheap ratchet screwdriver, the type with a fat handle that contains
the spare bits; it's 1/4" drive so if you can find one, you could cut a
piece of a 1/4" Allen key to use as an adapter. This one was free with 5
litres of oil but the same type of thing turns up in the pound stores and
places like Wilko, Lidl and Aldi.
Alternatively, Halfords used to sell BA box spanners, I have a set I bought
for working on valve audio gear which is full of BA fasteners.
Martin

Thanks for the suggestion. I might check out our local Aldi and if
there's a cheap screwdriver give it a go. I don't want to spend too much
in case the wobble in the two joints proves a problem, but I suspect
this might be the only way to do it. I don't think I've ever seen a
screwdriver handle (actually the ratchet isn't essential) which ends in
a male 1/4" fitting.

Best wishes,

Chris