Well you're already doing pretty well if you can consistently make £10 per race averaged over every single race. With around 11,000 races a year, you'd be grossing over £100k a year.
I should clarify, that I've only been trading since the summer and am nowhere near that figure - what I meant, was that when I started looking at horse racing trading, I found some videos online of an Australian trader making £10 per race and thought that was the holy grail.
It hadn't even occured to me that you could make more than that a race

Jimibit, great work on that trade, Sir!
Gives me confidence and inspiration for the future.