Broadband speed decreases when using test socket

[#1]

I have a long stnading gripe/suspicion tha the dozy Openreach engineer didnt install my new NE master outlet correctly before PN setup the BB.
My speeds have been poor but when on ADSL passable.  Now on ADSL2 I pay double for aan extra 0.5MBS if Im lucky.  When testing using the test socket then speeds either decrease or I loose BB although.  The connection to the test socket is loose and only works when tapped into place.
My router stats dont look to clever either. (From Thomson TG585 v8)
Uptime: 0 days, 3:44:05
DSL Type: G.992.5 annex A
Maximum Bandwidth (Up/Down) [kbps/kbps]: 16,979 / 8,020
Bandwidth (Up/Down) [kbps/kbps]: 440 / 7,695
Data Transferred (Sent/Received) [MB/MB]: 18.06 / 204.20
Output Power (Up/Down) [dBm]: 12.5 / 20.0
Line Attenuation (Up/Down) [dB]: 22.5 / 43.5
SN Margin (Up/Down) [dB]: 26.0 / 2.0
Vendor ID (Local/Remote): TMMB / IFTN
Loss of Framing (Local/Remote): 480 / 0
Loss of Signal (Local/Remote): 65,537 / 0
Loss of Power (Local/Remote): 0 / 0
Loss of Link (Remote): 0
Error Seconds (Local/Remote): 1 / 0
FEC Errors (Up/Down): 0 / 17,157,474
CRC Errors (Up/Down): 1,281 / 50,357
HEC Errors (Up/Down): 0 / 716,916
Is this my imagination or should PN support listen when I say I have a line fault?
Thanks

[#2]

Not sure what you mean by ADSL2 costing twice as much as ADSL  - The upgrade from 20CN to 21CN doesn't involve any increase in price as far as I know, unless you change your package.
As for the performance of your connection, it's obviously poor, but I would have thought that PN support would have wanted you to go through the usual fault testing on your side before either you or they decided where the fault lies.

[#3]

Jay
I have been through the PN customer support and they acknowledge the line isnt great but 'speeds arent guaranteed'  I was on a very good deal and convinced to upgrade by PN.  For some reason they hadnt migrated me onto ADSL2 until I paid for current package,

[#4]

Trying hard to visualise the problem you are describing with your test socket - if the "latch" on the plug is broken it obviously wont click securely into position in the socket, and if the gold-coloured spring contacts in the socket are bent flat or dirty that will of course make the connection very iffy, bearing in mind that the faceplate plugs into the same socket when fitted.
(Don't quite understand how the above could be a "fitting" issue though unless the engineer was extraordinarily cack-handed!)
Gently cleaning the contacts on plug and socket with meths and cotton buds is a good idea - if the spring contacts aren't projecting about half way into the socket space with the plug removed you can bend them up a little (not easy, you need to fashion a tool from a bent paperclip or similar.)