What an excellent business plan!!

[#1]

Probably worth doing if only to remove the router from the fault problem.
I am using the Netgear DG834G v4 (the one with the broadcom chip). http://dslsource.co.uk/details.aspx?idProduct=737&category=
Alternatively and assuming you don't want to enter into a new 12 month contact I saw this Speedtouch 585v7 for £24.56 plus £4 or £5 for delivery

However lets leave it for a few days to see what happens with the errors.
As you have a fault raised you may be able to get Plusnet to loan you one for testing but with that you won't be able to fiddle with the default noise margin.

[#2]

Thanks for that, I was thinking of this one http://www.netgear.co.uk/rangemaxnext_wirelessbroadbandrouter_dg834n.php for maximum range or do you think that is over the top and the one you suggested would suffice?
I will see how we go on first but the wireless is fluctuating badly now up and down the range. The noise is staying at 9.3 for now.
Sorry is the Netgear you use a modem/router?

[#3]

Sunny - It's a router with an inbuilt ADSL Modem.  It's one of the most popular ones around.

[#4]

Yes the DG834G is a modem router exactly as the GT you presently have.
Regarding the DGF834N I think you only get the range with the Rangemax series adapters not with your standard laptop wireless card.
The thing is that if increasing the noise margin fixes the error problem you could move the router back downstairs live with the lower speeds.
That is entirely up to you and depends on how critical the extra 500kbps is to you.

[#5]

Speed id not that critical, stability is for me but I usually connect with the cable when the router is in its usual place. I am using wireless because of children and I do not want wires running from the loft downstairs. And, these days if I can save money by either not buying a router or spending less that suits me fine. I am concerned that Plusnet wants to send an engineer though Oldjim, that was the last response I received today to the open question with them.

[#6]

Leave the question open - or add a note saying you are carrying out further testing.
Can you borrow a router to do a check to see if the speed, noise margin and attenuation are the same. If pushed send Jamesh a PM and he might be able to arrange something.

[#7]

Quote from: HPsauce

think about a filtered faceplate with ADSL take-off.

Worth considering again...... 

[#8]

Not sure how this would work with the master socket stuck in the roof.
One option which may be worth considering is the fit the filtered faceplate in the roof and connect the wires from the socket you use for the computer (but no phone possible) to the ADSL only connectors.
I am still not convinced that the problem is in the property given the results when connected to the test socket are just about the same as from the extension socket.
However you could invest in a bit of DIY and run a dedicated shielded cable from the master socket (with a filtered faceplate) with it properly clipped to the wall etc. so the children can't trip over it.

[#9]

Quote from: Oldjim

fit the filtered faceplate in the roof and connect the wires from the socket you use for the computer (but no phone possible) to the ADSL only connectors.

Exactly what I was suggesting. 
But then you fit a filtered extension-style faceplate on the local socket and can use a phone there as well if required. 

[#10]

[Censored] I had forgotten that the ADSL side was usually unfiltered 

[#11]

Sorry to be thick here but I am not sure what you mean by unfiltered socket/faceplate with ADSL taken off, or how I would get the telephone connected to a local socket or fit a filtered extension style socket.
I am fairly clued up with DIY and no worried about taking wires in/out and I also have the tool for connecting wires to sockets but I really do not understand what you mean, sorry. I feel really embarrassed saying that but might as well be upfront.
I do not know which are the ADSL only connectors either, as far as I know there are only two wires coming into the master socket but I could be worng there without double checking in the loft.
I do not know where I can get another M/R from other than buy one, and in Nov I did get one on loan from Plus but it made no difference whatsoever.

[#12]

Just to clarify, is your master socket in the roof an NTE5A - see http://www.buzzhost.co.uk/nte5.php ?
(some of your posts suggest it may not be)

[#13]

As many filters are in effect a low band pass filter in that it only stops the ADSL signal going down the voice line what has been described will work.
However reading the description of the ADSLNation filtered faceplate it would appear that it actually separates the low frequency voice part from the high frequency ADSL part

Quote

Accurate separation ensures that overspill is minimised. Overspill is where the ADSL signal leaks in to the voice frequency range or speech interferes with the ADSL signal.

from here http://www.adslnation.com/products/xte2005.php
If this is correct using a phone on the ADSL only extension may well not work - you could contact them and ask the question.
This is why  I suggested connecting the wires from the socket where you intend to have the computer to the ADSL only part.
The alternative, if you are willing to do a bit of DIY is to run a screened twisted pair Cat5 cable from the master socket faceplate filter to the room where you intend to have the router. This cable would be connected to terminals And B using the insertion tool and to an RJ11 socket faceplate at trhe other end.
This is the installation guide http://www.adslnation.com/downloads/docs/XTE-2005_Guide.pdf

[#14]

I'm pretty sure the unfiltered connectors are exactly that and carry both voice and ADSL signals.
But there's no harm in asking. 

[#15]

Now this was very well answered on one the posts here, complete with links to circuit diagrams ( for those of us that understand them  )
We really need a help page that distills all this brilliant help info..........