I,ve worked for both BT and Virgin,when Virgin brought out the 20 meg download speed we were told that it was not actually acheivable at the moment but not to tell the customer!They were in the process of sorting it but wanted the customers "now".
Getting the optimum speed depends on EVERYTHING being in A1 condition,from the house to the node to the exchange,fibre only gives you the best speeds if you have it from the exchange to your door,the bit of copper from the node to your door can drastically affect speeds if it isn't perfect,which in most cases it isn't.
With wifi there are now 2 channels available,called 2G and 5G,running on the 5G can avoid some of the problems associated with too many users being in the area,unfortunately at the moment it seems that it's only mobile phones that can run on the 5G side.I think a lot of problems could be avoided by simple communication,the trouble is most people don't talk to their neighbours these days,on my router there are eleven channels.Now if everyone spoke to each other then you could all agree to operate on a certain channel and stay on it and that would solve the problem for everyone.However if nobody speaks to each other then problems will arise,2 people are o the same channel and start hopping,they end up on another channel used by someone else and they too start hopping,and so it continues.If everyone was on a different channel and stayed there then half the problems could be alleviated.