@debs8 

Hi,

Has really only the broadband provider changed or has the switch to the new provider also necessitated a new router or "smart hub"?

In case you did get a new router from Sky, then test what happens if you unplug the new router's power adapter (power brick, DC adapter) from the mains socket. Does the Powerline light then come on after a while (give it a few minutes) or not?

  @woozle 

Thanks for the message and apologies for the lack of precision - yes a new router too.

The router and the TP link adapter were both in the same double socket. 

Without the router on, the extender displayed the powerline light. 

So I plugged the router into an extension cable instead of directly next to the adapter. It is now working fine. 

I suppose ideally a different socket would be better, but that is logistically hard. 

I suppose too much noise when plugged in next to each other for the powerline to work over the distance needed to get to the garden office?

Thanks again. 

  @debs8 

Yes, all electric appliances plugged into the mains sockets of one's home introduce some sort of electrical interference and noise into the electrical circuit.

How strong that interference is and whether it affects the performance of Powerline adapters varies heavily and it's impossible to predict it in advance.

A power adapter of manufacturer A might not affect Powerline at all, while a power adapter of manufacturer B could bring down one's Powerline network.

It's great that you've found a solution that works for you.