The part about the customer buying their own parts, really from any source seems have become a big "NO NO" for many garages, a bit annoying for some of us, but I've had that response when I wanted a new ABS sensor fitting and then the car being MOT'd, initially that hurt a bit, but I had to accept it, really not too good as I grabbed a new ABS to carry out diagnostics - and ECP was the easiest place to buy a Bosch one from - £67.99 PIM price was under £15, but that would have taken maybe 3 or 4 days to land on my doormat!
Leaking DCC dampers, especially the LHS front ones, hum, yes, a common problem it seems like, SEAT at least, fit Monroe at factory, and the difference in price from a Monroe branded DCC front damper and a Monroe VW Group branded DCC front damper - at least for a 2019 SEAT Leon Cupra is huge - horrible.