Speed tests are notoriously unreliable.
Yup. I hate it when people quote speed tests at me. There are so many factors outside of your own ISP that could affect results that they are very much pointless.
As I say time and time again on here, its not about the speed, its about the quality of service. Two broadband services which are identical on paper can have a vastly different feel.
Had satellite internet fitted for the same reason - we only getting 0.8 mb/s due to cable run distance. Total outlay £800 fitting plus £49 p/m.
However, now the speed test says we are getting 19.6 mb/s, but it takes 3 times as long to download stuff!
You also have to be aware that stuff like Tooway is a 30:1 contention product and, perhaps more importantly, is not FAP free. So it might be their filters that are performing the first act in killing you off rather than bandwidth or latency (which will finish the job, as mentioned earlier).