David, the issue is around the parts are not available, in this case the thermocouple.
By all means if you can show me a suitable thoughmocouple, I am happy to see if this has a suitable Gas Council code which would make it compatible with your appliance.
From my research no such parts are available for your unit, if you secure parts from a donor unit from a scrap yard (which I think is your best bet) the appliance can be repaired, but you will not find any gas safe engineer who will use any 'universal' parts which is not certified by the gas council, as the liability sits with the last gas safe engineer who commissioned the appliance.
Your only option as I see it is to find a suitable part, if you send me the GC (Gas Council) code of the 'universal' part, or the details of the donor part, if it comes back as compatible, I can find someone to attend and replace the part.
I know this isnt what you want to hear, but when is comes to safety and liability no trustworthy engineer is going to risk bodging an appliance for making an extra £50, in effect it would be criminal.
I hope this clarifies why your unable to find an engineer able to assist without the parts being made available.