Cotswold - Webasto Problems

Being new to motorhome ownership, we were in Scotland last year when we experienced our first lock out, and it cost £40 to call out a motorhome technician to solve the problem. ( I watched as he removed all the fuses under the passenger seat, waited, then replaced them and reset the system to get it working again) Recently, refilling the system after the winter drain down, the unit started overheating and locked out, so I repeated the removing of the fuses etc and reset the system and it started to work again, only to overheated and lock out again. I contacted the supplier of our motorhome who said that they did not fix the heaters and put me on to Electro Diesels who are Webasto agents. Staggeringly, the quote to repair the unit was £1220. It required a new blower motor and cabin thermostat, both of which have to come from Germany, and heavy labour charges due to being mounted underneath. Having warranty on the motorhome, I thought ok no problem, but the insurers have limited their exposure to £1000 for any single claim, leaving me to pickup the balance of the repair cost.
Feeling that I am being screwed, I would like to know how much Autosleepers paid for each new unit when fitted, as I am sure that it was nowhere near the repair price quoted.
Has anyone had a similar experience?