kev,
the rod may be a Butterworth.
I use Berkley Trilene on mine - its a low stretch nylon so not a good idea if you have a tendency to throw rigs when casting - good anti twist properties - virtually nil memory, doesn't go brittle - but costs some $$$.
A lot of blokes think Platypus is good stuff too.
All this twist & Alveys stuff is such crap. Make sure you use an appropriate swivel - not to big - & make sure the sinker doesn't foul it from working either by leaving a longer tag on the knot between the sinker & the swivel or I put a small colourless bead above the knot between the swivel & the sinker.
Once every 6 trips walk 100m of unrigged line down the beach - wind it in with your rod tip up.
I reckon threadlines put more twist into nyon with their smaller spool diameter & right angle lapping motion to respool.
chris