Keith:
Coilifying straight leads:
I tried Gypsy's method and got moderate results. He suggested wrapping the straight lead around a knitting needle but that's something we don't have, so I used some old bonsai branch forming wire. This is thick guage (about 4mm diameter) and can be easily bent into any shape which is useful in securing the ends of the cable to stop it uncurling.
What you do is: Arrange for your former wire to have a straight section at least 12" long with turns through 90 degrees at the ends. Secure one end of the cable to one of the 90 degree ends - I used cable ties - so that the cable can't twist around the wire. Now start coiling the cable tightly onto the straight section of the wire so that it looks like a coiled cable. When you run out of cable at the other end, secure it to the 90 degree bend at that end of the wire.
Place the assembly such that you can get access all around the coiled cable and get a good hot hairdryer playing on the coiled section. Get the cable as hot as you can with the hairdryer - you're unlikely to damage the cable within the power limits of most domestic hairdryers. Try to get the coiled section of the cable as evenly hot as you can. This'll probably take some 10-15 minutes.
Now leave the assembled cable and wire former to cool naturally. Leave it for at least 24 hours.
Unsecure the cable ends at the 90 degree turns, straighten the former wire and slide it out from the cable. You may need to manipulate the coils a bit to allow the wire to slip through and clear.
The first time I tried this on the two cables we use for the intercom the result looked very impressive. However, the first run out using the newly coiled cables demonstrated that the coiling didn't stay fully in. There was enough relaxation of the coils to allow the cable to stretch and then get itself twisted up in a bit of a knot! This happened to both cables equally.
Undaunted, I went through the same process again but tried to get the cable a lot hotter, and for longer, than I did the first time (as per the above suggestions) but haven't had a chance to test them out yet. They do seem to have more 'spring' and when stretched do return more or less to their coiled state but we've yet to use them over a protracted period where they will be held extended.
Worth a try though. Do let us know how it works out for you.
BTW, the cables I have are Maplin's 5-pin DIN socket to plug extension leads. I suspect that different lead manufacturers may well give different results, some better than others.