I took from the earlier thread that a 15” paper coned model is the way to go. Is that the HPD you mention?
All Tannoy the classic Tannoy ranges have at least a 12” and a 15” driver, and it wasn’t until much later (i.e. long after Tannoy changed hands) that anything other than a paper cone was available (IIRC the DMT 12 was the only large driver with a plastic cone, and after that they returned to paper).
Basically there are no ‘bad’ 12” or 15” Tannoy drivers, and each size has their fan base. The 15” tends to have more air-moving ability and dynamics, the 12” a slightly clearer mid-band. You also need to factor that the classic London Tannoys (Blacks, Silvers, Red and Golds) are very collectable and valuable, you will pay a lot more to own these than the later drivers, and as a rule of thumb each preceding generation is worth twice the former, e.g. Reds 2x Golds, Silvers 2x Reds etc. It is also worth noting that some of the later Scottish-made ranges such as the Super Red Monitor, Super Gold Monitor have nothing whatsoever to do with Reds or Golds! They are ‘80s 38xx ceramic magnet drivers.
Basically you need to do a lot of reading as it is a company that has, in some form or other, been around for a very, very long time. You definitely need to find your way around the history, models and historical context to some degree, though if you are using a high-power solid state amp I suspect you will be perfectly happy with the more recent and more affordable HPD and later ranges. Don’t rule out new either, if I didn’t have a very nice pair of Golds in Lockwood cabs in the front room I’d be hugely tempted by a new pair of Ardens as they seem very good and there is no risk or faff involved in getting a perfect pair (vintage Tannoys are notoriously variable when it comes to pair matching etc), so you can certainly spend a lot and not be happy. It is also getting far, far harder to find nice clean examples as most of the decent ones are in Japan, Hong Kong or South Korea by now!