How can you replace the box without touching the backplate/wiring?
The socket belongs to Openreach. I'm sure Sky could arrange for Openreach to replace it (wouldn't be cheap, probably just over £100 IIRC).
They aren't difficult to replace, and I'd risk it (and keep hold of the old socket so I could put it back if I ever needed to).
Also I have sky.. so even if they sent an engineer out they wouldn't know i fitted it would they.. could have been owners before me lol..