Sorry to hear about the speed problems you're experiencing. I've checked your connection and I can see a fault in your area that's responsible for reducing the speeds during peak time hours (evenings and weekends). The fault ref is: F004519657 and it's due for review on the 15th March.
I do apologies for this, if you post back to us on or after the review date, we will be more than happy to provide a progress update.
Thanks for your patience,
Tech fan? Have you read our Digital life blog yet? Check it out