Wifi connection but 'No Internet Access'

Question

We recently had BT fibre optic BB fitted and all seemed well on the day.  However very quickly devices using the wifi started to have only intermittent ‘connection’.  The devices show as having a good/strong signal, yet are often unable to access the internet, and in the case of our lap tops when we can not get online they say ‘Connected’ to the wifi but they also say ‘No Internet Access’.  The iPad minis we have also show as connected, with good signal, but just will not access the internet.
The issue is intermittent and has no set pattern.  At one point all devices are connected, sometimes one or two aren’t, sometimes none are.  When they will not connect we have to move them into the room where the hub is and wait for them to reconnect.  We are talking about 2 laptops, 2 iPad minis, 2 smart phones and 2 Xbox 360’s, as well as my PC (which is connected via ethernet cable).  So I doubt I'm overworking the hub, especially as my old router worked (just) with this amount of devices and that was on a basic non fibre optic BB.
When the engineer connected us he set the internet up in the study, which is at one end of our house, as that is where the master phone point and my PC are.  He connected the PC via Ethernet cable and I connected an iPad mini wirelessly (whilst sat next to the hub).  He did not check anything else worked or check if we had coverage in the whole house.  I do have a phone point in the hall, which is in the middle of the house, but he did not offer to connect to this point, or suggest that may offer better coverage in my house. 
My frustration with this is compounded by the fact I had a basic Netgear wireless router running on a bog standard Virgin Media BB connection, never stronger than about 3 megs, that covered the whole house from exactly the same spot as the Homehub. 
I have tried adding a plug in signal booster (as suggested on another thread), and that has helped with the overall strength of the signal in the rooms furthest from the hub, but it does not stop this ‘connection’ issue.
Can someone help with suggestions regards settings on our devices or the hub, I did wonder if it was due to the dual frequencies the hub uses, or regards getting someone out to look at this.  I am at my wits end already, and I have only had BT BB 5 days.
Thanks in advance.

Answer 1

From reading your original post, the issue doesn't seem to be wth wireless signal strength - your devices are connected to wireless but just can't make an internet connection, correct?
In my experience there are a number of reasons why this can happen:
1. Your device has a fixed IP address and it's on a different subnet from the router.  Are your devices configured for static IP addresses or DHCP?  The BT Home Hubs use 192.168.1.x as the default subnet.  To be honest, it doesn;t sound like this is your problem if they work when moved to a different location, but best to check.
2. Your hub isn't connected to broadband.  You should be able to see this from the 'b' light on the hub.  Again, doesn;t sound like your problem.
3. The device connects correctly to the wireles hub but fails to get an IP address.  You can check IP address assignments on the hub itself by pointing your browser at bthomehub.home, going to Advanced Settings and then DHCP Table (this is for a HH3).  You can also check the IP address assignment on your laptops, but I don't know what OS you're using so I can't tell you how to do that.  If the device is failing to get an IP address then I'd try restarting the Hub.
4. Your devices are connecting to the Hub's BTWiFi network instead of your real network (this happens regularly with my iPhone and iPad).  Force a reconnect to your real network.
Hope this helps!