@TonyL 

Hey Tony

Sadly its likely the multigang socket you are using is causing the issues, they dont work well when ran through the multigang / trailing lead.

The model you are using is an older model now (AC1) and it uses just one wire connection for data transport, the newer AC2 standard uses more.   One of the main issues with the older model is due to the lower number of wire conenctions it is a lot more susceptable to interference and will stop working quicker, i feel this is what has happened to you.

Your best option sadly may be to considering upgrading to the newer AC2 model, specifically one that has a passthrough port.    Passthrough will allow you to plug the multisocket you have into the homeplug itself and this wont affect the performance.

Something like the TL-PA7017P may be of interest to you

  @Philbert Would I still have the same problem though having to use a multigang socket to plug the router into the TL-PA7017P along with my other equipment?

Also I need at least three units and dont seem to find any that are sold seperatly so I guess I would have to bin my existing four and by four new ones

  @TonyL 

You may get away with only one of these plugs

My thinking is the newer AC2 standard is much improved in respect to working with Multigangs so might provide you a better signal. 

  @TonyL 

I did purchase the unit you suggested but again its size does not allow me to plug it direct into the wall socket

do you have any other advice please?