Hi Gavin,
I'm with Greg here
. Go the Astrosystem or the Howie Glatter.
I've got the 2" Astrosystem barlowed Laser collimator and it works a treat. Its also well built.
As Greg mentioned, when collimating the primary you need to tweak the primary knob, stand up and look back in the focuser and do this a number of times. It can be a slight pain the backside and much easier if someone is around to help.
I've put up with this for a year or 2, but I've just ordered the 2" tublug from Howie Glatter (around $126AU posted) and hopefully it will be arriving soon. It's compatible with the AS, so when it does arrive goodbye to having to crouch, tweak primary knobs stand up and go back to the top to check the focuser etc (and repeat 4-5 times). It can be all done crouching down at the rear of the scope and done in less than a minute.
End of the day, imo, buy quality and you won't regret it.
Cheers,
Norm