I can't really answer the question, but if you are suddenly getting daily disconnects I would expect the cause to be between the cabinet and your computer. There's a slight chance it is E-side of the cabinet, as my problem was, but you haven't given any info on what you and BE have done to try to trace the fault.
I've replaced my filter and the cable that connects it to the router. I can't try my other router due to BE's bridged method of providing static IP addresses - my only other router doesn't support this.
I had BT do a line test, and that came back saying that no faults were found.
If the fault is D-side then unless it is your router or filter it is going to be even worse with FTTC and you will get a screwed-up connection. So I feel you need to find it.
BE had me change the profile to 'reliable' and that resolved the disconnects. They then closed the ticket.
BT will guarantee me a minimum of 16Mb down (but no up guarantee), which is the main reason I'm considering this move. Zen say that their contractual minimum is 12Mb which again, I could live with.