Toby wrote:

To verify this, put a normal lamp in (maybe two) and see if this cures it!

If this is the case, then you will need to either leave the circuit with
a micture of lamps, or chnage the transformer for a lower wattage one,
but make sure if you decide to switch back, you put the old one back in,
or you will probably end up overloading the smaller one!

Thanks for reply Toby, it may be impracticable to replace the
transformer (cost wise) as I cannot get to the wiring to get one
transformer to supply multiple bulbs and one transformer per bulb would
be costly.

Geoff Lane