Where can I get a heater block unit for a dolphin 1000?

I have tried Shower Doctor who have told me that you cannot now get dolpin shower replacement parts for love nor money. We have a dolphin 1000 shower with a defective heater unit. Simple enough to replace but where can I get a new unit from? I have tried Dolphin's head office in Manchester and all you get back from them is an automated message that 'all our adivisers are busy or are on annual leave and that someone will call me back within 48 hours'. After past expereince with Dolphin, I suspect I will never get that call. Anyone know where I can reliably get a new heater unit from?

Thanks