I've decided to go for the Asus DSL-N66U, I'll post my experiences on here in case it helps anyone else.
OK, I ordered the Asus DSL-N66U, vdsl modem and router, I've had it for about 3 weeks and I've returned it.
Initial setup was easy, looks smart and the gui is very good, pleanty of features. Very nice.
But, the initial sync was about 7mb less than the homehub, the WiFi did not drop out at all, but the range was at least half of the homehub. The wired connection was very fast and when I was in range, so was the wireless connection.
The new beta firmware did not work, I could not access the internet from any device, went back to the latest stable firmware.
Also, using the network monitor built in to OSX 10.10, the HH5 identifies as GB, the Asus would only ever identify as DE, spoke to Asus about this, they were puzzled. Asus support were pretty good when I messaged them, just don;t ask too many questions in a single message, that confuses them.
The sync speed kept dropping, down to 50mb, I usually have between 69 and 73! Plugged the HH5 back in and immediately synced at 63, I'm hoping it will rise back up to what it should be.
So the Asus is winging its way back to Amazon and once i've been refunded i'm going to try the TP-Link W9980 (£65). I hope it performs better than the HH5, unless they send me an actual brick it should be better than the Asus.
Just to note, this 'review' only refers to the Asus DLS-N66U (£105), not the DSL-AC68U which is a LOT more money (£180) and seems to get good reviews.
I'll post again when I have had the TP-Link for a while.
I've now been using the TP-Link W9980 for over a week and have good things to say.
The WiFi, is strong and stable, excellent, reaches the whole of my house and has fair transfer speeds.
The VDSL connection is stable, the only disconnects have occured when I have restaarted the router, very good.
I'm running a beta version of new firmware and it rocks. It supports G.INP, which I think is part of the low sync speed with my HH5a. I have learned that the cabinet that I'm connected to is a Huawei cabinet and most likely has had G.INP implemented recently. I have read (can't find the link, but it was n the interent so it must be true!) that he HH5a does not support G.INP, apparently the HH5b does, and without G.INP support people have seen a large drop in sync speed, I saw a 20mb drop in downstream speed during feb and a 4mb drop in upstream speed, overall a 20%is drop from a stable connection of 13 months.
After 8 days running the beta firmware which enables G.INP on the TP-Link, my upstream connection is back up to 19mb and my downstream connection has risen up to 66mb, another 6 and I'll be back to where I was in January.
I would wholeheartedly recommend this router.
As a bonus, BT can't mess it up with dodgy firmware either, then ask for £129 to replace the router that they wrecked.
I hope this helps other people looking to replace their HH5 router.
thanks for update - I am sure that will help others who decide to ditch the HH5