
I repaid mine early when my mortgage statement showed that my endowment would be large enough to cover it nearly two years early.
They did take about 6 weeks to do it though.
What they did was have my account running as a £1 owing to hold onto my deeds.
Now that the deeds have gone electronic they will be sending the physical ones back to me, as their physical possession is no longer relevant.
I'd ring them as things ought to go through automatically, but don't cancel a DD, a there may be minor amounts due (say a partial month etc.