The maps dont seem to be able to list resellers .
Looking at my locality the speeds I obtain ( both from my old ISP ADSL24 and my new ISP Vivaciti ) are way above those shown on the map
My technical knowledge isn't really good enough to start giving advice, but if you think you should be getting better speeds than you are then I'd suggest you start a new thread in this forum, giving at least the results of a BT speedtest (assuming you're not on LLU) and your router stats.
If your speed can be improved, there are plenty of people who can tell you how to go about it.