It's a bugger, all told.

Get the car up on a lift and look towards the rear, just by the
back box of the exhaust. There's a metal heat shield there. Remove the two
bolts holding that on, and you should be able to see where the two halves
of the brake cable connect to the handbrake line. There's going to be a
nasty 'orrible rusty lump of metal there that was at one time a bolt and
casing type arrangement. Spray this liberally with WD40 or other
penetrating oil and scrape madly with a wire brush. Eventually you should
be able to see something that looks rather like the brake calipers from
a bicycle. What you need to do is unscrew the nuts on this arrangement so
that more of the bolt is within the casing (You'll see what I mean when
you get under there) therefore making the brake cable shorter.

If you have trouble finding it, I'll try and get a reasonable-ish picture
of mine.

John