I have a Sky Hub Router which is in the office as this is the location of the master telephone socket. The router has an ethernet cable plugged into an AV500 Powerline Adaptor with pass through (TP-PA451) the other paired power adapter is in the living room about 25 meters away. This other adapter had an ethernet cable which fed an old DLink wireless router that I configured as an access point. I have another pair of powerline adaptors (TP-PA4020P) which are each paired to the one in the office. One is in a bedroom on the upper floor about 35m from office. This two has an old router configured as an access point. The last powerline adapter is in a garden shed connected to a switch which connects a PC and printer.

This setup has worked fine for 4 years but one of the old routers is now playing up. Requires regular reboots. Also it's a bit of a pain when moving about the house having to change which access point to connect to. Some devices will automatically disconnect and connect to a stronger signal other do not. 

We are a big techy family and have some 60+ wireless devices already.

I've purchased a pack of 3 Deco M4s and would like to understand the best way to network these around the house.... The shed section is fine as it is. I would like to do it in such a way that we have one SSID for the whole house if possible. Also the main reason for the powerline adapters is that the main Sky router was located at the far end of the house. I think I would still need to use them with the Deco units.

Any advice would be appreciated. 

Below is a rough representation of my current setup