since i changed my rear light clusters the fuse which feeds them keeps blowing (have now gone from a 10amp to 15amp to 20amp) will buying and installing lower voltage bulbs cure the problem??? if so what wattage???????????
interested to here from people who have done the conversionor anyone who can help

I'd retrace all your wiring just to be sure of any loose conections.
you could also try the l.e.d bulbs wich only pull 1/50th of the power of a normal bulb. you can find these on ebay or in performance car shops.

Personally I would be looking for an unexpected earth somewhere in the lamp or close to the wiring.

As for fuse size. Watts = Amps X Volts
therefore Amps = watts / volts

Add up your total wattage (all the globes that come on at once) and divide it by 12 (volts) and that should tell you the amp draw that your indicators will achieve.

As a very quick example, my vehicle has on each side:two 21w front and two 21w rear indicators and a 6w side light. Thats 90w. Divided by 12 gives 7.5 amps so the original 10 amp fuse should be more than adequate to handle the power draw.

Putting higher and higher fuses in can lead to some other major problems like fires or smouldering wiring.

little update
disconnected bumper lights and installed 10amp fuse again no probs whatsoever have now installed led front sidelight bulbs and connected bumper lights up again all working ok
now just wait and see
if it blows looks like it could be a problem with original bumper lights