very slow speed for a few days now

[#1]

Hi guys
have recently seen my connection speed go up from 1.5mb to almost 5mb which was a great surprise and i have been browsing and downloading at a faster rate for a couple of weeks.i dont know why that suddenly happened i guess BT may of upgraded my line somewhere however a few days ago it has gone back down to 1.5mb but my router still shows my connection being at 4998kbps.I have done a BT speedtest which gave me the following results:
Download  Speed
1.47 Mbps
Download speedachieved during the test was - 1.47 Mbps
For your connection, the acceptable range of speeds is 1.2 Mbps-4 Mbps.
IP Profile for your line is - 4.41 Mbps
2. Upstream Test:  -provides background information.
Upload Speed
0 Kbps
 
0 Kbps 448 Kbps
Max Achievable Speed
Upload speed achieved during the test was - 0Kbps
Additional Information:
Upstream Rate IP profile on your line is - 448 Kbps 
just wondered if anyone could help on this subject
thanks
chris

[#2]

I've just run some checks for you and can see a line synchronisation speed of 4998kbps, the line rate is currently at 4409kbps. Your connection also seems quite stable so I can't really see any obvious issues that could be casing a drop in speeds.
Your best bet for issues like this is to raise a fault with us: https://portal.plus.net/apps/kbdfaults
Let us know if you have any difficulties after you've raised the fault.