Opall II shower blows a fuse when using the higher temperature?

Hi I have had the shower for 14 months and recently it blew all the fuses in the house so I had an electrian check it out and told me i would need to replace the cabling with a 10kw which I did, but the shower still blows a fuse when using high temp. The electrician told me he would get me a part which he said is a Thermostat and heater pot. He keeps fobbing me off saying they are trying to trace this part. I have just looked on the internet at spare parts for triton opal II and I cant see this part anywhere. Can anybody please help I just cant afford to get another electrian in at a cost of what!! I feel I am a woman who has been ripped off by another unscupulous workman. I hope not,but thats how I am feeling at the moment.