Hey Graham,
Depends what you are looking for and how serious you are? Wired or wireless? Budget? ect...
Taking a stab I would have to say that a Davis would be the go if you are looking for something better than the OS(WMR-200) you have, they can be pricey when purchsed onshore but can be ordered from the US for quite reasonable prices(I can dig up exactly where on that one if you want?), anyways here's the info on them from the home site...
http://www.davisnet.com.au/
I'd recomend staying away from the La Crosse series, they are not really indifferent to the OS's, being that they are pretty much cheap junk that's not priced so, for a basic amateur they are ok, don't get wrong they do have thier place in the market but having been a user of one for years... when it comes to more serious measurement of the weather, they also have thier place in the bin! LOL!
Of course if your looking to lash out big dollars($700+) there are more advanced setups that I can point you to if need be...just let me know if you want more information!
Cheers
Lee