So, having been told by some drooler on BT Sales that TotalCare wasn't available for residential lines, I ranted about it on Twitter (*).
Surprise, surprise, someone from BT just called, within the promised two days, to confirm I wanted it and to tell me that it'll be applied to my line from the end of this month.
Thank you to the people on uk.d-i-y who told me about it and pointed me at the BT price list where it states that TotalCare *is* available for residential lines.
All they need to do now is fix the current fault (broken for the second time since the 1st July) and I'll be a little happier. I particularly 'like' the fact that even though it broke again within a couple of days of being fixed the first time, the 4 day wait starts again.
(* Yes, I am on Twitter. Not in my real name, of course.)