@pippincp: Yes, I know about star-wiring, thanks. When I say "your own home" I do include the BT wiring within your home on the supply side of NTE, not just the consumer's internal wiring. Indeed they're most likely to be on the BT side.
Lucky me then! Hopefully, it is something that they will spot and be able to resolve. I'm happy with my speeds because they are still 4-5 times better than what I used to be able to get, but as this will be my max for the next, however many years, I'd like to get the best I possibly can. No point settling for lower speeds if there's higher to be had.
So, on the DSL checker, on the Bridge tap column i went from a "U" to a "Y" about a week ago when I made the upgrade to Infinity 1. And my speeds were in the impacted range. So I guessed the bridge tap was the cause of my problems. Now i've checked again and now it is down as "N". How can a bridge tap suddenly disappear overnight with no physical intervention?? Bit annoying because it was something that could be clearly shown to BT that something is definitely wrong on my line. If the bridge tap was fixed then surely my speeds would have increased but I'm currently on 21 down and 0.4 upload. This is getting very frustrating, to say the least!