I have an Orchid single line PABX - mainly as a means of boosting REN, however found when I fitted it that my main telephone, a 2-line Delta 700 - with one line connected to my VOIP adapter, the other via the Orchid PABX to our BT line, would not display the BT CLID, but the VOIP CLID was OK.
Apparently this problem was due to my Delta 700 requiring CLID to conform to the BT standard exactly - http://www.sinet.bt.com/sinet/SINs/pdf/227v3p7.pdf
whereas some telephones can accept both the BT style CLID and other styles. The choice of CLID that I have with my VOIP adapter Cisco PAP2T is amazing.
I recently looked into REN boosters which do not affect CLID, this was easy when UK telephones were 3-wire, since REN boosters including the BT supplied one simply boosted the ringing capability on wire 3 the Orange with White Band wire. However now that telephones including BT supplied ones invariably just use 2 wires, 2 & 5 the BT REN Booster fails miserably. The only 2 wire REN boosters that I have so far located are from the USA. Again, similarly to the Orchid PABX the "better" one receives and then re-transmits to line the CLID info and since intended for the USA market, would fail to work on the BT system. The more basic one that is available works in a different manner and will according to their product engineer not interfere with CLID of any style. (Boosting REN without upsetting CLID is not rocket science, I designed a unit but declined to build it for use on our telephone line due to BT's obvious dislike of anything not type approved.)
Getting back to the OP's problem, it certainly sounds like a settings issue within Talk Talk.
Andrews & Arnold FTTC
DrayTek Vigor 2920Vn
Andrews & Arnold Data SIM