Thanks for the posts. From the stats that you have posted it doesn't look like you have been restricted as BT will only restrict your speed if you are on BT total broadband option 3 and go over the fair usage. The restriction would be to 1MB but only at peak times so I don't think this is the issue. You would have received an email as well.
If your connection constantly drops out then the equipment at the exchange will think there is a problem and automatically lower your sync speed to try and stabilise your connection. Your IP Profile is determined by the sync speed as IanC has pointed out. I feel that the real problem here is the dropping connection, if we can solve this problem then the sync speed and IP profile in theory should sort themselves out.
An increase in noise interference could cause your broadband connection to lose sync. Have you tried plugging into the test socket as IanC suggested? Does your connection still drop while plugged into test socket? I can check the network side of things, please drop me an email to email@example.com, include your BT account details and the link to this thread.