My experience is that most instructors are happy to talk flying (and that includes groundinstruction) for most of the day, as long as the student is interested and well-prepared.
May be that on a very busy day there is less opportunity for this, but on most days, in most schools there is plenty of opportunity to talk and learn.
And if there is something which takes a bit of extra time, just be generous and pay for that bit of extra tuition. An extra £20 here and there goes a long way for most instructors and is money well spent, if you compare it with the amount of aviation time it can replace.
FD