slow connection speed

Up to the last few days my connection speed was always between 3.5 & 5mb but the last 3 days it has been stuck at 2048kbps during this time the noise margin has ranged between 12db & 16.5db so clearly the connection speed should be a lot faster. I phoned sky to find out what was the problem, they mentioned they were doing tests on my exchange and in another 3 to 4 days it should return to normal. Any idea's what these tests are about ?

Could be sonething to do with this:
http://www.skyuser.co.uk/forum/sky-news-announcements/22335-sky-perform-spot-adsl-line-management-some-300-000-lines.html

They might have placed you on a fixed speed so they can accurately measure the noise margin as part of their exchange tests.

Home ADSL: Sky Max
Business ADSL: ZeN Office 8000