Thanks for all the replies, particularly Ryan.
In the end I've given it to a mechanic. All going well I could have done the job but if there was an issue it would take me time to sort it out, especially as I haven't changed a brake pad since the mid-80s (the HJ47 was all drums and I haven't had to touch the HJ78). It was booked in to get the air con fixed anyway, so I added the brakes to the job.
And with the time I saved I got a pile of mulching done
.