There are typically about 550 go-arounds per year at Heathrow. I've heard it said that if the figure was lower then it would show that the controllers aren't doing their job properly
It's always worth looking at them on the WebTrak replay. On the evening of last December 15th there were 3 consecutive aircraft sent around on 09L, which is very unusual, though alas they have now scrolled off the end of WebTrak's 3 months' history.