Just a cautionary note here:
You're in Australia, which is now having its Spring season. A rose's petal-count during the Spring flush can be misleading. Most of my roses (hybrid-teas) have a lot more petals-per-bloom during their Spring Flush than they do in later flushes. For example, in Spring my Double Delight has 50+ petals, and my Peace tends to have 60+ ...significantly above the "normal" number during the rest of the year.
So... your rose's petal-count of 50 is likely to be lower in later flushes.
Hoping this info is helpful,
JohnReb

Thanks JohnReb,
That's very helpful,
I had noticed that to some degree, but didn't realise it could be such a big difference, we have had more rain this Spring so everything has an effect I suppose,
Thanks for your reply,
Yvonne

I have had my rose confirmed as Acapella by a rose enthusiast who also has this rose amongst his hundreds of roses, so it has been solved,
Thanks, Yvonne F

You may already know about HelpMeFind dotcom (for rose-info). If you don't know about HMF, take a look at HMF's webpage for Acapella (at the following URL, or use the hotlink at the end of this post). Be sure to click the Photos tab on that webpage, to see additional photos of Acapella.

http://www.helpmefind.com/rose/pl.php?n=28617

By the way... I'm not disagreeing with the rose enthusiast who said your rose is Acapella. I do agree. I'm just saying you can get additional confirmation at HMF's Acapella webpage & photos.

Regards,
JohnReb

Here is a link that might be useful: Acapella at HelpMeFind dotcom