I may have missed something, but Im only aware of 2 versions.
I'm led to believe that the new UK versions contain the BCM63137. Not that it makes any difference. If you go to the Broadcom website, BCM63137 auto redirects to BCM63168. I also asked TP link what was the difference and was told something along the lines of nothing much, its the same family.
Therefore it wont make any difference to f/w etc.
Ive not actually opened the case to see whats in mine. I just went off what the guy at tp-link who sent out 4 to various kitz members who beta tested it said. I dont know if b*cat ever got around to opening his either.
Actually I just checked my email from TP-link : This was from a few months before we got ours and before we beta tested supposedly what I thought was the v2.
VR900 v1 uses BCM63168 SoC, while we have version 2 in developing which uses BCM63137u SoC(same series with BCM63138)
Actually now Im very curious what is in ours. I'v just pulled the unit out of its box, but cant see any easy way to get in it. B*cat / Ronski / Jamie do you fancy trying to get in it. Unfortunately I have a knacked hand which is why I dont do internals, and also why I dont even build PCs any more. Im happy to look if its something simple like screws but this isnt. It looks like the front cover may pull off if you hook your finger nails under it. It possible it has some retaining clips under the bottom edge, but despite trying, I've not been able to pull it open. :/
Aside from the modem chipset the rest of the hardware should be the same.