Thanks for the responses All!
It didn't produce too much, though more than I was expecting - about 8 cups in almost 10 metres of chimney. It was used from the end of September till the end of April pretty much non-stop and this was the only cleaning in that time. I don't have anything to compare to, but that doesn't seem too bad, especially since the previous owner wasn't exactly a fire wizard.
I'd love to build a
RMH, Glenn, and not have to spend another day doing
that job! I have the perfect space for one, I think, but am not sure what the insurance company will say about it... Once the financial shock of moving here has worn off a bit, I'll look into it. I'm also considering a wood cookstove in place of the one that's here. Which is not that old, btw - you can't get insurance here with old-timey stoves. Or mortgages...
Be nice to dispense with both of those things, but that's not how it worked out.
Right, time to stack some more wood!