You need to post stats from your router - if hh5 then go to troubleshooting then helpdesk and post stats
run btspeedtester and when first test completes then run diagnostic test and post results. Must be done with wired connection
enter your phone number and post results. Delete phone https://www.btwholesale.com/includes/adsl/main.html
BT do not cap or throttle P2P.
The previous thread that you posted on was with regards to legacy users of BT broadband and did not affect new users such as your self.
Have you tried a Glasnost test to see if they are?
Can you give more details about what is happening when thing slow down. Is it a cretain times of the day, is it when you are using any particular site etc etc.