0.1uF capacitor in series with 1 ohm resistor, fitted to the LV feed. It'll work best near LED or transformer, try both to find out which.
NT
Thanks NT, You may have realised by now that me and electrics don't really do together too well. So, when capacitors and resistors get mentioned my eyes glaze over. Your advice is much appreciated but it's going beyond the level of simplicity I was naively trying to achieve. Would it make a difference if I swapped out the original transformers for some of the 12V DV drivers instead ? I don't really fancy rigging up the arrangement you mentioned myself - I'm sure I'd end up doing something else odd :)
Cheers, Keith