B)

However, it would be different if you said: they were used to being in love, weren't they?

See the difference?

Yes I see.

So, the negation refers to the verb "use to" and not to "to be".

My logical comprehension told me so but my feeling for language rather preferred version A).
It is still in training. ;-)

Thanks anyway. :-)

Perhaps one day the extended use of "innit" (meaning 3 in Wiktionary) will catch on in standard English, making life easier for learners. (;-)

And with a bit of luck it won't! ;-)

Slightly OT:

When I worked in EFLT, we used to have a grading test for new students. It had various components and took about an hour to administer, and some time to mark. Someone then correlated the marks on the individual components with the marks gained on the whole test. One component involved adding the correct question-tag. This component correlated very closely with the whole test. As it could be done in about two minutes and marked even faster, we wondered whether we shouldn't ditch the rest of the test. We did in the end keep it, but only because we feared that the students might think we weren't being thorough. (The other very good correlation was a specially constructed dictation.)