Thetford N3175 fridge freezer fault

hi my motor home is a 2015 model and while we were away in Cornwall this September our fridge became faulty .it would not work on the 240v  at all . This problem started some time in the night .when we came to get something out of the fridge everything was warm ,

we found a Thetford dealer and there engineer was on holiday so they  got some one Elsa to come, he found the fault in no time and told us he has had this before ,

he replaced the control module and it is work ok now , the engineer said as he does not work for the company he would need to charge me ,  it cost me £159.98  he said if I send it back to Thetford company they will send me a replacement as it is still under garantee and they should do this ,

but Thetford company will not honour the guarantee as it was not one of there engineers 

and there are more engineers around Devon and Cornwall .

i told them that I did what the dealer offered me ,as am disable and us a wheelchair it is hard for me to get about and having to look around to see if I could get another engineer that would come to me. 

I think Thetford company is mean all I wanted was a replacement as I can not trust it will not do it again,I bid not ask for the money  ,I now have two gauges to read the temperature at all times