The nearside indicator causes brake lights to flash in time. offside works correctly. There is a ryder towbar component spliced into the wiring which contains a beeper that also goes off in time.  Any ideas on how best to tackle this?  I did replace the hazard button unit (aftermarket brand)  to cure another problem a while ago. It isn't a problem with the bulbs or their housing because I can remove these and the towbar beeper still still goes off. 

M

Either ground wiring problem, or check you've got right bulbs in the right holders or not correctly fitted.

Trace/check all the ground (0 volts) wiring. A multimeter will help...

@MarkyD - As xman says. My first thought was of a bad earth or reversed stop-tail bulb (it can be done with sufficient brutality) on the LH rear cluster.

Thank you. No doubt I will be back with more questions after having a look with the multimeter tomorrow.