I just noticed that you are from the UK. Before that, I assumed what you meant by bullfrog was the American bullfrog, Lithobates catesbeianus (formerly Rana catesbieana)
Yeah, just when I think I have names figured out, a nice sharp kick to my hind-end is given to me. What happened to the genus Rana? Sorry, I can't spell none too good
Rana is still around, example Rana aurora is still Rana aurora. I believe, though I am not 100% sure, that it was Darrel Frost that changed it in 2006.