I live in Nunhead - Ivydale Road area and we've been experiencing the same issue. Have called them today to complain again and told they're aware the issue has been on going since APRIL 2015 with a date for fixing it of 30th MARCH 2016. So a whole year of paying for 50mg download but only getting around 10mg with it sometimes dropping down to 2mg. The fella I spoke to was up front about the problem they have with 'High Utilisation' saying its worse between 6 > 12pm, essentially anytime you want to use it when you return from work. They would only offer me ?7.50 as a refund and not back date. As they are in breach of contract and unable to provide a service that's been paid for I explained I'll be terminating my contract with them and notifying Ofcom.