Next installment..
Tried updating to 3.8.2.1_BT (txt says Modem Code: VDSL 576D17 / ADSL 572801) and it gets borked again.
Currently stable on 3.8.2.1_VT2 (but not plugged into ADSL at the mo)
DSL versions: 574307_A/B/C HW: A / 571801_A HW: A:
... will see how it goes...

It would be nice if the previous UK versions (at least the one before) were available

I thought so too, I am still convinced that there used to be a .uk archive years ago but I cannot find it now. Looking at the release notes I don't think that there was a 'BT' version of 3.8.1.

I *think* that the vector 3 releases are (almost exactly) the same as the BT version but I have no proof for that. It certainly seems to look exactly the same when you run it. Irrelevant for me because (on the three 2860s that I use) the lines round here will only remain stable with VT1 versions anyway. It has to be something in this part of Essex because three 2860 routers in three towns all act the same (ish) both on good and marginal VDSL lines.

I agree it's a bit of a state right now.

I have a 2760n which was on 3.8.2.1 vt2 (don't know why..) on ADSL. Now have "fibre" so thought would upgrade to 3.8.2.3 and downloaded the BT version which trashed the 2760.. (3 quickly flashing lights). Managed to find the ftp site (ftp://ftp.draytek.com/Vigor2760-Delight/Firmware/v3.8.2.3/) and loaded VT2 by tftp with the recovery tool.
Router is a "Delight" version.
.. why should this happen?
.. is the _BT version same as _STD on the ftp site?
.. there obviously is some mismatch here but I can't find anything about it.
.. how do I know whether to use VT1/2/3/4 ?
.. am i forever barred from the _BT version?
confused .. :?
TIA

BT and STD are not the same. BT versions have all the additional requirements for BT's SIN498 approval.