Apologies for not posting for 7 years but I'm a little confused.
Searching for another Tmax I've come across three 2nd hand 2016 Bronze Tmax's, with keyed ignition, extra little light in the fairing etc. I thought the Bronze was only out in 2014, and keyless ignition and lack of small light came in 2015.
Just wondering if Yamaha had a secret stash

Yamaha are very good at releasing secret stashes of Tmaxs after a new model comes out - it seems to happen every time! So it wouldn't surprise me if there are Bronze Max's registered after you'd expect.
In any case, there seems to have been some fuzziness in the transition between mk4 and mk5 Tmaxs anyway - I did look for a 'post-reg' mk5, but there seemed to be both 2015 mk4s and mk5s.

I did ring a dealer who was trying to sell one for £8k and they just pleaded ignorance

£8k for a 2 year old secondhand one??? You can buy a brand new one for £9k (if you can haggle hard).

Haggle hard ? these days of PCP my local dealer laughed when i asked about a cash deal, even a couple of dealers up north wouldn't go under 10.5 k though this was the DX model.

I think the situation is that Yamaha have stocks of the old model left over at the time of model changeover, possibly through over-ordering. This was certainly the case with the Mk3s. So, you can find early models registered late. We have a family of Mk3s (2008-11) two of which which we bought new up north in Summer 2014 (so with 14 plates). The were 2/3s price and with full warranty. Similarly, I have a 2008 model MT-01 which was registered in late 2010 cos nobody wanted to buy it!