How is this any better than just getting 100/10 or higher? Apart from it being slightly cheaper...
The UK network is known for its massive overload, primary during peek hours. Demon now has implemented Quality Of Service (QoS in short) for gamers, prioritizing gaming traffic by matching the type of traffic and putting this in the priority queue. Said differently, your gaming traffic will route trough the network as if you were the only one using it (figure of speech).
Not sure how this works out in real life, but it should at least guarantee low latency until the network border (prolly some Internet Exchange)
Simply getting more bandwidth is not the solution if the backbone network is not suitable for it (which apparently in the UK is the case), too much overbooking and shit.