A good way of monitoring the speeds is to go into Windows Task Manager > Performance > Wi-Fi > Resource Monitor.
The monitoring process and actual measurements are of course, only as good as the sampling rate.
However, at least it puts your mind at rest that the pc performance is ok, and Wi-Fi connection is actually doing something!
As a further update, there are some wireless routers which support up to 600 Mbps Wireless-N at 2.4 GHz using 40 MHz channel width but with only a 3x3 antenna configuration. One example is the Netgear AC1900 D7000 router.
These use 256-QAM modulation which provides a 33% increase in data rates compared to the more common 64-QAM. This means that when using 40 MHz channel at 2.4 GHz with 802.11n, a max data rate of 600 Mbps can be achieved using either a 4x4 antenna with 64-QAM or using a 3x3 antenna with 256-QAM. The BT Smart Hub test report states that the 290 Mbps data rate achieved on the Smart Hub at 2.4 GHz with a 3x3 antenna uses 256-QAM (but only a 20 MHz channel, otherwise it would go up to 600 Mbps) and was tested with a Macbook Pro laptop with 3x3 antenna, but to get the benefit the Macbook must also support 256-QAM.
256-QAM is used as standard at 5 GHz with an 802.11ac adapter, hence the speed increase of 11ac over 11n, but there are very few client systems which support 256-QAM at 2.4 GHz because this is not compliant with the 802.11n spec and is regarded as a proprietary extension (for now at least). It is a bit misleading of BT not to emphasise this in their test report.