Openreach have doubled my Broadband speed...

[#1]

Excuse me IanSn see reply #20.
TV & recording studios are a TOTALLY different kettle of fish from ADSL. Laying ADSL cables out straight next to mains or anything else carrying noise such a SMPSUs is the very last thing you want to do.

Quote from: Anotherone

As for tidying up the wiring, well to be perfectly frank, if you are not tripping over it, I wouldn't bother. Wiring that is randomly strewn about like that can be less of a problem than if it's neatly coiled up or running for lengths alongside other stuff. As all this lot is now filtered from the ADSL anyway, it should be even less of an issue. Now, power supplies may, and note I said may be an issue, if they are what's called switch-mode and are on their last legs, but that is something we can check out separately later on.

[#2]

@Anotherone
Missed that... 
Knowing nothing about ADSL cabling I bow to your better knowledge.
Nevertheless, I've read many threads on here talking about interference from external sources and crossed mains cables will generate noise making fields in anything that can be effected by them. Laying them straight reduces this.
Where you have electrical tangles like this one, perhaps bundle mains cables separately?

[#3]

Coiled cables can produce magnetic fields, they can also increase inductance which can sometimes have undesirable effects.
Laying wires parallel can increase coupling between them. Laying phone cables parallel to mains cables is definitely NOT recommended.
If one has to, then a minimum of 6" apart BUT if the interference is strong on the mains even that may not be enough. Cables crossing esp. at 90° is often ok.
My rule of thumb is "if it works, leave it alone". His sync speed is pretty good for the attenuation, so the conclusion has to be it's working quite well, so leave it all alone and see what longer term stability is like.

[#4]

Quote from: Anotherone

There doesn't appear to be any markings visible in the pic, I wonder if it has any? You have to dig well into Belkin's own spec. to see it's TP (twisted pair) to Cat5 standard  A bit like some of Belkin's other products (eg. modem/routers), a bit deficient with ability to find details.

Belkin Pro Series High Speed Internet Modem Cable www.belkin.com E204816 (UL) Type CM 75°C 24 AWG Cat5 Lan Cable 13660