Just replied via PM regarding servicing the watch etc.
I tried one of the aftermarket inserts when Cousins started selling them 4-5-years ago. The insert fitted nicely and the colour was OK, no problems with that, but the finish was printed rather than anodised and was nowhere near as durable, I remember thinking it would flake off if it got scratched.
I don’t know what the current offerings are like but I wasn’t impressed. I explained this to the owner and let him have it for free.