Universal Playback dont own it at all.
Its a BBC series and the BBC have licenced the show to Playback.
However the planned series 3 dvd was due out in June but never came out.
The Xmas special on there is nothing of the sort.
The last episode of series 3 just happened to be aired on Xmas day---its simply the final episode.
All 3 series are listed for release next June -but dont hold your breath.
The 1984 special the OP wants is out of circulation.
It contains a great deal of Beatles music and the BBC have been unable or unwilling to pay for clearances beyond the original airing.
The BBC never repeated it and UK Gold did schedule it in the early days but it was pulled before broadcast and never aired.
The same problem affects it on dvd which is why even though all 3 series should be out on dvd next year , the special wont be.
UK Drama have rerun the show a number of times recently and they also miss out the special.
Someone out there did record it when broadcast and copies of that recording were made available on vhs and dvd via ebay.
Look out for it