Re: SMEG A42 need repairs
£65 labour is very reasonable for a dual fuel appliance. It costs a lot to CORGI certify an engineer for gas work.
Main oven fan assembly part number 6992500763 retails at £32.91 excluding VAT & P+P
Grill thermostat part number 818730033 retails at £45.99 excluding VAT & P+P
If both of these parts need replacing then you’re looking at about £100 in parts costs.
As to what you can do; if the machine is out of warranty then very little. Appliances can and will fail at some time, it’s just a question of when. Some unfortunately fail faster than others, often without apparent cause.
In all honesty I don’t think either your retailer or manufacturer will want to become involved in this. It will be up to yourself to arrange for a repair to the appliance.
You can try Repairs@ for a local engineer from the UKWhitegoods database