One room slow with dLan

I have a home network set up using Devolo 200 AVPlus plugs, one at the router (ground floor), one to serve an office on the first floor, and one to serve a studio on the lower ground floor. Wifi works well enough in some parts of the house, but not in the two rooms where I have installed the plugs.

The system was working well for the first few years, but more recently has stopped working acceptably in just one room - the studio. It works, but way too slowly (around 1mbps) for things like Skype. We even have to be patient with simple internet searches. I cannot think what has changed in the environment.

I have tried reinitialising the Devolo plugs, and tried swapping them around (plug from fast room to slow room), all with no success. Moving the Devolo plug around, I have shown that all the sockets in the studio give a slow connection, but sockets in other rooms on the same floor give acceptable speeds. EIt seems as though something might be amiss with the electrical circuitry, but what could it be, and why would it have changed suddenly?

Any suggestions gratefully received...

The software that comes with the plugs should let you see the connection speeds for the various plugs themselves

Is it possible that neighbours have plugs too and the two networks are close enough to interfere in the one room?

Having used Devolo products myself for many of years I know they can be very sensitive to other electrical items being used, even to the point of making a big difference if you have an extension cable being used in the same room.

Devolo do have a new 1200 range which are a lot better than the old 200 ones, but to be honest it would be cheaper to run some cat6 cable instead

Thanks for the suggestion, but I doubt that it's interference from neighbours, because: i) the neighbours are not especially close; ii) the room affected is no closer to a neighbour than rooms which work; iii) judging by the poor wifi reception in that room, it is not particularly susceptible to radio interference.

I am living in France,and the electrical installation looks unfamiliar after decades of UK houses. There's a frighteningly large number of MCBs on the consumer unti, and I believe the supply to the house is three-phase, with the house circuits being distributed evenly over the three individual phases (I'm no electrician, so I trust this makes sense). I would suspect that feature, if it were not for the fact that the system worked for a few years.

I did wonder if I'd have to run some ethernet cable. Obviously I bought the dLan system to avoid that hassle, and I am still hoping to avoid it. The cable runs would be long and tortuous, and all the floors in this house are concrete...

It would not surprise me if the plugs do not work so well between sockets connected to different phases. Devolo do claim this is possible.

In reply to a post by masala:

I did wonder if I'd have to run some ethernet cable. Obviously I bought the dLan system to avoid that hassle, and I am still hoping to avoid it. The cable runs would be long and tortuous, and all the floors in this house are concrete...

That's one of the main reasons why I've had to run my network cabling outside, though it does look neat and tidy especially compared to one of my neighbours sky dish cabling

In reply to a post by Michael_Chare:

It would not surprise me if the plugs do not work so well between sockets connected to different phases. Devolo do claim this is possible.

Yes, that can be a problem with 3 phase supply.

An option might be to place the plug in a room near to the studio (where speeds are good), and attach a wireless access point here. Then hopefully in the Studio the WiFi would be fine to use.