Thanks gg30340, that's really helpful and I suspect that's the problem.
I guess I'll just have to hope a problem occurs at some point along the line that means they come out and fix the issue though I suspect that might mean we end up with more joins rather than fewer.
Probably best to hold out for 5G I suspect...
Thanks again, I really appreciate your help.
He definitely is!
I can't ask him to post his stats, but I saw it for myself and the thinkbroadband website confirms it. (The same website gets my connection speed dead on, so I've no reason to doubt it). Even if you don't believe me, BT's own adslchecker shows that he has at least 50% faster speeds than me and he's 33% further away!
I wasn't looking for an argument, but I'm grateful to the one person who has responded positively and it sounds like it's probably to do with the cable type and joins that's reducing my speed. That's all I was after - a plausible explanation.
If anyone else has anything positive or helpful to say, I'd be glad to hear it.