Hi Craig,
Firstly I suggest you join
www.trailersailerplace.com.au/ and talk to them. The reason I say this is a trailer sailer is more than the boat. It's the trailer ,which can cost to fix , and it's what loads your vehicle can tow. Getting it surveyed will not cover the trailer .
You need to decide if you want a swing keel or drop keel . They both have their pluses and minus .If the keel is cast iron be wary of rust . read up and ask questions.
The Timpenny above looks a cracker and could be bought for a couple of grand less than asking I reckon. They are pretty quick.
BTW I sail a Sonata solo in my old age and love the advantages of a ts.
You can even take it home to play with

Terry