A question - but a conclusion first; just to complete this thread for anyone thinking of same stuff.
I studied the youtube video for flashing the device to upgrade it from ADSL to VDSL. then I got scared. Lots of people having trouble and a few modems bricked. Plus I would need to get a USB TTL cable for £6 off ebay.
So. I got an open reach modem of ebay for £10 (buyer collects). After a bit of fooling around (a lot actually) I daisy chained the OR and the router. And that is the set up I am communicating through now.
The question: there are TONs of settings in the TD-W compared to the HH5 - I have mirrored those I know about - would someone care to indicate the most critical things I should care about please (on a scale of noob=zero to geek=10, I'm about 5. Be gentle)