dante- :
7ms is the command prompt ping from me to my isp which i guess it should be near 0?
No not really, my experience is in the uk, but it will usually be about 10-30ms on adsl.
Make sure you are pinging the ISP and not the modem.
You may wish to try an extended ping between yourself and the ISP when your line is quiet.
ping -l 1200 -n 200 [ip of isp], look for packet loss.
It is possible you had contention issues. ADSL uses something called a DSLAM which connects up to 50 telephone lines to the internet. if too many people are using the internet heavily at once the single up link from the DSLAM becomes busy and you get latency. Its quite possible they moved you to a quieter DSLAM.
The BRAS is the Broadband Remote Access Server. It is the computer in the exchange that decides how fast your line is capable of going and handles authentication etc when connecting.
I think what is more likely given what you are saying is that they have tweaked, your noise margins.
Basically you have a copper wire and you send a broadband signal down it at a range of different frequencies. As the signals travel down the wire, they start to distort or get interfered with from radio waves and thermal noise. This will happen to a point where the signal starts to become unusable. This happens in stages with the outlying frequencies becoming unusable first. your modem can cope with this to some extent and will only see some errors. It will work with the computer in the exchange the BRAS, to select the right values that your line can handle. Sometimes, particularly if your line conditions fluctuate or have a minor intermittent fault this doesn't work too well. Its very hard and expensive to improve the quality of a line like this, so the next thing ISPs will try is manually fixing the line with safer margins on the BRAS. Because you are using a slightly narrower frequency range there is less bandwidth to use but if it works its much more reliable so it's worth the trade.
You mentioned that this started when the ISP upgraded to higher speeds? This could be because they enabled a higher range of frequencies for use, but this just made the problem on your line worse.
The alternative explanation would be the contention issue I already mentioned getting worse.
I would say if your connection issue stops, accept the lower downloads and be glad you have a more reliable connection.
If it still happens check your internal wiring, and filters etc. I don't know of you have a test socket available?
http://bt.custhelp.com/app/answers/detail/a_id/13567
Also listen for interference on your phone line, this could indicate an issue with bad wiring or filters.