You didn't answer my questions.
If you can send photographs it may help a bit.
Another option may be to cut and extend the conduit.
Are we talking about twin and earth cable, or single core cables? Another question, I am sorry.
If it IS singles, why don't you draw new longer ones in? Afterall, the main point of circular conduit is that it can re-wired easily. Though you mention a junction box (besa box?). You can of course join cables by crimping.
