Hmm, well, you're on a Broadcom cabinet
DSLAM CHIPSET VENDOR : < BDCM >
My experience was that my Draytek 130 modem and the broadcom cabinet which is only about 100m away really didn't like each other. I had 80/20 sync speeds, but with multiple - 5 to 10 - resyncs per day. I don't know if it was relevant, but my lone had vectoring enabled which I don't thnk play nicely between the chipset in the Vigor and the Broadcom chipset.
So, I gave up, sold the Vigor and bought an old Zyxel 8924-B10A for £20 on fleabay, installed lovely custom firmware from here to enable jumbo frames and vectoring, use it in bridge mode, and now have a line which sync at 80/20 and has downsteam SNR of 14db and it hasn't dropped at the moment for 20 days. I'm monitoring it with dslstats and after a bit of fiddling, even managed to get the 2 VOIP ports working.
So, for what it's worth, I found Lantiq chipset in the vigor, which I believe is also in the HH5, didn't like staying synced at high speeds on my very high quality line. I'd have been happy if it dropped the sync speed a little to become more stable, but it refused to do that - even if I manually increased the desired SNR. So long as you don't mind a little firmware installation and a little telnet fiddling around (to discover the supervisor password), then I'd say it was by far the best £20 I've spent in a long time. I even bought a second one and shoved it in the cupboard in case the first one packs up before fttp comes to my neck of the woods (or I retire, move to the country etc., which I think may well be sooner!).