Many thanks Percy for such a prompt reply.
Upon closer examination of the Skyleader TX it does appear that this particular model held 2 x 4.8v Nicad batteries (there are two plastic 'straps' in the shape of 4 cell AA packs. I owned a Fleet 35Mhz set up (circa early 1980's) and I do know that had two 4.8v Nicad packs in the TX, but I believe that the charging system differed to the Skyleader units.
I'll be patient for a while and see if a knowledgeable person online can help me, failing that I will contact Mike Ridley as you kindly suggested. Thank again
Chris Coe