Kayne,
I also own a South African Wheatstone 30b Anglo. I've had to buy every concertina I own without getting to try it. I bought it from a guy on ebay. He emailed me a couple of sound clips and I bought without the luxury of getting to play it. I also bought a concertina once and then returned it to the buyer. I spent a lot of time going through the process and paid the shipping both ways. Playing the concertina has definitely been an investment of money! Good luck with your search.
Cheers,
Nate