Tony
Not necessarily. Some old radios e.g. Futaba M Series, Simprop had a signal pulse width of 1.3ms at neutral c/w the almost universal modern standard of 1.5 - 1.52ms, and no current ESC would work with one of those sets. If your radio is a Futaba with three wires to the servos and a plug shell which contains little brass sockets (as opposed to 3 brass pins which stick out of it) then a modern ESC should be OK. If you're not sure then best to hand it in at the nearest Police Station, apologize profusely and you might get off with a caution................. If it's an ACOMS then better to leave it by the roadside, at night and somewhere quiet, as there are severe penalties for owning one of those.

A brand new 5 channel 2.4GHz set will give you change from forty quid.
Dave M
(If anyone knows of a 'Spreading Ripples' smiley then could they please send the link to me and Andy Nightingale?)