No, it is available to me. It has been available since 2011 (I believe) but I have no need of it.
A basic TalkTalk ADSL2+ service is more than enough for what I use the circuit. Due to the line attenuation, I have configured my end of the link to operate in ADSL2 (not 2+) mode.
What would be ideal for me? What is my wish? A simple symmetric 5/5 Mbps DS/US service.