Many thanks for your information on this problem. I used to have a Home Hub 5 and everything worked fine. But....
Got a new Home Hub 6 two weeks ago. All 9 devices connected wirelessly no problem. But within 24 hours my Sky on demand dropped out and I couldn't reconnect. Contacted Sky who (after 2 failed attempts) sent me a new Sky Wifi connector free of charge. Still wouldn't connect. Spent half a day trying almost everything in the book under the guidance of Sky Technical Support (rebuilds of my sky box, software update, reboot router, etc. etc.) but to no avail so Sky booked me an engineer visit for a couple of days hence.
In the meantime I knew the only thing I hadn't tried was a Factory reset of the Home Hub 6 - which worked so thinking I had resolved the issue, I cancelled the Sky engineer visit. But next morning I was faced with same problem again - connection had dropped out and wouldn't reconnect. I wasn't prepared to Factory reset every time I got this problem so I phoned BT.
BT told me that maybe I had too many devices connected and I should try disconnecting some of them to see if that solved the problem. At this point I was advised to contact Sky as since all other devices were connected Ok it was a Sky problem.
While chatting to BT I had been browsing this forum and discovered your posts so on being told it was a Sky problem, I pointed out that there were people on the BT forum who had offered solutions. I was then advised how to change the BT hub settings according to Cliff's posting. BT told me this would solve the problem but if not, I would have to contact Sky.
Following the change of the hub settings, I manually configured the Sky box network settings as per your post, and Hey Presto, the box connected to the router instantaneously. Problem hopefully solved but I'll have to wait and see if it is a robust fix. Will post to let you know how it goes.
I have no idea why Sky didn't offer this solution, or why BT somewhat reluctantly told me how to change the router settings. At one point I was hovering over a big hole that seems to exist between the 2 companies when certain faults occur and one blames the other.
That said, whilst I don't consider myself a techy, I do have an IT background and it helped enormously when people start talking about IP addresses, subnets DNS etc. But wouldn't there be loads of folk out there who would have simply struggled with all this and no doubt ended up spending lods of money on Sky and/or BT engineer visits. And how long would it have taken to resolve the issue I wonder?
Anyway, rant over! And thanks again - wish I'd discovered this thread 2 weeks ago!