Advice following PAT testing

Maintenance

Good morning.
I recently had an annual PAT test on my 2 properties. Both properties have 2 portable appliances, and both also have integrated ovens. The company were informed of such.I was not present, and the visits were organised by the company, direct with the tenants.
I think 2 different PAT testers did the 2 properties: at one property, the PAT tester did not include the integrated Oven (which has always been the norm), but in the other property the tester did choose to include it (never before been the norm). He failed it on not having heat resistant flex. The flex used is what is normally used if an Oven is hard wired in.
I am just wondering where I stand on this. Never before have they tested the Ovens in either property because they did not class them as portable appliances. Both cookers have flex and plugs on, but, as described, they are classed as integrated.
Are you able to advise if I need to get the wiring on the failed one changed? I feel a little backed into a corner by it. I have had the property for four years, and it has never before needed a test. There will be a call out fee by an electrician of £45, which is going to be a significant expense for a very small job. Could my partner (who is competent, but not an electrician) change the flex?
Thank you in advance,
Kind regards
Christine