1. I use an APC UPS as well, and I filter the _output_ from that. Reasoning - the pseudo-sinewaves from these things can be quite ugly staircases. I use a Belkin PureAV mains unit, and more recently a second layer of conditioning filtering beyond that is about to be fitted. Total paranoia.
Ok - I've bought a well reviewed Tacima extension lead.
2. I have a couple of split-doughnut ferrites (ebay, or Maplin) on the dc supply to the modem.
Done - just waiting on delivery from China.
1. I notice you're running one dect basestation off the NTE5. I had to *double-microfilter* mine, I used a BT Pressac faceplate, and then added an ADSL Nation dangly filter in before the phone. The reason was that it used to stuff the SNR everytime it went on-hook->off-hook.
Ok - I can't say I've had a problem when the phone goes on / off hook, but I have a bunch of spare (ISP supplied) microfilters so why not.
2. About the 5m of internal wiring. I decided that it would be extremely worthwhile to move my NTE because of the pickup of electrical noise inside the house. You're right that 5m seems nothing after the huge length that's gone before, but your signal is v weak and local interference sources relatively v loud. That was my thinking. So that's my other tip for wasting another > £100 of your money. :-)
I'm going to have to disagree here - my setup is typical, BT phone cable comes along road on telephone poles, down the front of the house and into the ground floor. It doesn't go around the house or anything.
It could come up into the loft or upstairs and save me a couple of m of cable, but not only would it be very impractical, but I also can't see it making a difference - I had an ancient "junction box" and some bodged internal wiring replaced with a new socket and cable from BT, and lost about 3m of phone cable in the process, and got no improvement. At least it was free - I can't justify paying £130 to get them to move it (nor do I want them to).
I also got a Netgear DG834 v3 as per your recommendation (gotta love eBay - £6.50 delivered). Currently syncing at 800kbps, which is pretty decent - for reference, my Billion has been stuck at 640kbps @ 5db recently, and I've been unable to get back to the 700-ish range I was at before (yes, I've been keeping 5 days between all my disconnects). Will let it run for a few more days and see how it goes.