Not sure about my line profile

[#1]

I currently have a download speed of on average 9Mbps, it was averaging around 10.5Mbps until a couple of weeks ago.
Looking on the BT Broadband availability checker it's telling me the following -
Our test also indicates that your line currently supports an estimated ADSL2+ broadband line speed of 17.5Mbps; typically the line speed would range between 15.5Mbps and 20Mbps.
Does this indicate I have an issue with my line/master socket?

[#2]

It could be one of a number of things but that is a good thing to focus on from the off. There is an easy way to rule that out however.
If you're able to get one of us members of staff to perform a line test whilst the router is connected into the test socket (assuming you have one) http://www.plus.net/support/broadband/master-socket-guide.shtml that can help us identify an issue with the socket or your internal wiring.
Otherwise if you are able to post your router stats, both whilst in the test socket and in the master socket (again assuming you can do that) then one of the forum regulars or mods may be able to advise you over the weekend.
Adam.