Acoustic cover mountings

Hi people

I have what looks like it might be a fairly common with the acoustic cover mountings on the Td5. The two bolts on the exhaust side of the engine screw into a pair of blind holes drilled and tapped in the cylinder head, and they seem OK. The bolt on the inlet side of the engine screws into a captive nut on the fuel cooler mounting plate.
Unfortunately the captive nut is no longer captive and it seems to turn as the bolt is being screwed into it.
The original captive nut is a round type, one with the serrated edge to hold it secure when it was pressure fitted.
There is a replacement captive nut as far as I can see, part number PYH100400, but it's a square type, and as the old saying goes, you can't put a square peg in a round hole.
Does anybody have experience of repairing the captive nut system on the acoustic cover mounting bracket please and if so, how did you do it?
It would appear to me to be folly to start waving a welder around near the fuel system.

wouldnt a helicoil or maybe rivnut insert do the job?

Thanks for you reply @sierrafery mate. I can't see a helicoil doing the job, I wouldn't think it's a suitable job for one of those. As for a Rivnut, that seems to be the kind of thing already in use.
Seriously, I think it's going to be a case of finding a way to square off the hole in the fuel cooler mounting plate and fitting one of the square captive nuts PYH100400.
Being basically a lazy animal, I was hoping that somebody could come up with an easier way of doing it.
It's OK for now, just a little job for the future.
Thanks anyway.

The simplest solutions are always given by lazy ones , i'd just drill a suitable hole and fit one of these rivnuts: