We have 9 or so older A320's without brake fans, and a good number of new A319/320/321's all with fans. When the decision was taken to purchase the 31's (last to come) the engineering input was the 320's WITH fans had a lower brake wear than those WITHOUT and that the extra cost of the fans would be reclaimed over time due lower brake wear.
On regular LHR-MAN's during summer time you can find it hard to keep the temps low due short turnarounds.