For ease, go for Powerplugs for the interim. Distance is not an issue under 100m and although I use Solwise I understand Devolo are the 'favoured ones'.

Yes, Cat5/6 is the best solution, but if that is difficult use HPs. For best performance use them on the same circuit, athough they will cross circuits at the distribution board or consumer unit, but same circuit will give best performance. Consider a wifi Homeplug on any network to feed anything far away from the router.

I have found that switching noise on the circuits used for Powerline networking can cause problems with momentary drop-outs that are not a problem for most applications but can cause VPNs to drop.

My wife uses a VPN extensively from her laptop which she uses to work from home. This works fine when using the WiFi or cable direct from the router. For a part of the house remote from the router we have a WiFi access point connected to a home-plug 500. We can stream BBC iPlayer endlessly on this as well as all the mobile devices, however the VPN drops from time to time on this setup.

The circuit used covers all the ground floor sockets which has the TV, computer, fridge, microwave and hi-fi connected. We tied down the VPN drop-outs to devices on the circuit being switched on and off. Presumably this is creating noise on the circuit that is momentarily knocking out the network. I have a VPN system on my work laptop that can cope with that, but my wife's VPN setup seems much more sensitive.

I've just got a pair of TP-Link AV2000 adapters to test at a specific problem site. I'm not at home at the moment but when I was, I was getting about 150Mbps across two circuits via the consumer unit and much higher when on the same ring.

When I get back I'll run some more tests and let you know.

The connection seemed to be reliable with no packet loss. It did vary throughout the day but it's currently in an electrically noisy environment.

Depending on the speeds, a fix could be a good WiFi extender instead of homeplugs (but expect speeds to be around 20/30Mbps only) or running an ethernet cable.

I personally have found the same issue with homeplugs in every house I've lived in. Random little drop outs which affect some services.

Speeds were stable for about a week and then they dropped suddenly from about 150Mbps to about 25Mbps.

Power cycling the homeplugs restored performance immediately but it's still a disappointment after such a solid start.

Well, the update is that things seem to be working better than I expected. The site I've put the TP-Link AV2000s at is a large and old house. At a distance of about 45 metres, and with mains wiring of dubious provenance, I can transfer files at 43Mbps.

That may not seem great but there are some internal granite walls three feet thick which mean wifi is hopeless between rooms. The internet connection is now the limiting factor - a grindingly slow 1.2Mbps down and about 300kbps up.