Hi Stephen,

For the benefit of other users of the website reading this, a category C write-off is classed as repairable, but it was written off by the insurance company as they deemed the repairs not to be economically viable. There's a wide spectrum of what that might mean as it depends massively on the value of the car. It does not necessarily mean that there is anything wrong at all with your car now, assuming that the repairs were carried out correctly. 

Nonetheless, as you've discovered, others may be wary of buying your car because of this, which is not something you were made aware of before you bought it. You should in the first instance get in touch with the Competition and Consumer Protection Commission (CCPC - ccpc.ie) to establish your options before taking any further action or contacting the dealer you originally bought the car from.