Thanks guys. I was told it was female by the guy... but wanted a second opinion just to be sure.
The most amazing thing is... she was given to me for free!

Just the cost of a coach ticket to the Midlands, which ain't bad. The guy who gave her to me didn't want her all on her own and thought she'd be happier in amongst my group and so gave her to me for her own welfare. Not interested in the money. It's nice to know there are people who really are more interested in the welfare of the fish.
I've seen evidence of a little scrapping since she's gone in, not on her but on another fish, the sex of which I'm unsure of. Saw some red marks on the body and shredding on fins. No sign of infection though and the fish seems active and normal so I have left it in the tank but am keeping a watchful eye. Hopefully just good clean water will be enough to help it heal quickly.
You should see my alpha male now. He's GIANT. He dwarfs the others in the tank. I'd hate to be on the receiving end of his temper if he ever decided to unleash it! He's got a giant fat body and huge sail-like fins which he displays proudly. He's a gorgeous beast.