So they charge around £200 for nothing more than an annual oil change and a poke around your motor looking for stuff to fleece you for, they then tell you that they don’t actually do the job properly and you need to spend another £20-40 for a “flush “.
The “ flush “ is doing nothing that couldn’t be achieved by getting the oil nice and warm before draining it, and if you’re really meticulous, perhaps flushing with a tiny bit of fresh oil.
Surely they’re taking the pi55.
I’d suggest doing the job yourself if you’re really concerned about preserving your engine.