The traffiic management TalkTalk use on their LLU network (Plus and essentials products) should not affect TV stuff like iPlayer and netflix. Additionally the actuial main menu pages for a service like iPlayer are very small and should quickly.
General rule is to believe that the last thing changed before it stopped working is the primary cause.
What speeds do you get from your talktalk connection normally?
Looking at maniual, do you have Acquire IP address and Acquire DNS address set to auto? What happens when you do the Connection Test?
The Veira server may be the issue, others reported problems in January, that have continued for some for a while.