Just changing our own quarter panel after a small ding below the light cluster.
£400 to knock the dent out and respray, £600+ VAT for the complete quarter panel including the corner panel, £220 for the corner panel alone.
Bumper off, inside trim out etc etc and there's a LOT of fasteners.
We ended up buying a secondhand quarter panel off ebay, taking it off the quarter of the car that came with it

was useful, as it showed us what we have to do on the car to get the panel off.
It is all bolted and screwed plus lots of sealer, the only welds are between the main quarter panel and the corner panel, and if you replace both then the welds don't need to be disturbed.
The used one is in the painters now.
I'll probably take some pictures when we do the swap.
Peter