Varying download speeds

[#1]

For a number of months I've been plagued with wildly varying download speeds. In early December they were around 2800 kbps. I went away for 7/8 days to find them at 300 kbps on my return home. By the end of 2008 they's finally eased up and settle at around 1700 kbps. Then, during January, they drifted up to around 2900kbps. Then suddenly in early/mid February they dropped back to 1700 or so. 3/4 days ago they went back up to 2900 and have remained there :-). (All taken from http://www.mybroadbandspeed.co.uk/ although other speed check sites confirmed the readings failrly closely.) On impulse I downloaded a CSV file from the 'History' page which displayed a vast range of IP addresses and that all the sudden changes in download speed corresponded exactly to a change in the IP address. I generally, but not always, leave the Netgear DG834G router/modem on 24/7. It's within a metre of the incoming BT socket fed by a high-quality filter with only a single corded 'phone attached. I realise that a Dynamic IP means a changing IP but why the wildly different speeds associated with each IP address?

[#2]

Have you looked at your router ADSL stats to see if your sync speed has been changing when you are not switching you router off. You can expect that your IP address will change when you boot up or resync.
Also when you re-sync you may have unfortunately synced at a low speed which will lower your profile and hence throughput.
Check you current Profile at the member centre https://portal.plus.net/my.html?action=data_transfer_speed (login required). If this is inconsistent with your sync speed, run a BT speedtest to see what you profile is.
Maybe if someone from PN reads your post they can check your account to see if you've had any low sync speed events previously.

[#3]

Thanks, I'll keep an eye on the router/modem sync speeds as well. In the meantime, whilst the speed is fine I'll simply leave the route on 24/7.