Brs normally has 10 based aircraft, 9 A319's and 1 A320!
BRS have had 2 A320s already for about 3 weeks already, and 8 A319s. We currently have G-EZTW And G-EZUK based at BRS. the 11th based a/c that will be coming in will be a third A320. And there is deffinately no spare aircraft at BRS at the moment.
And with the 11th aircraft to be based at BRS this summer, they always do bring another aircraft in for the peak summer season, they certainly have done the past few summers anyway. So it's normal and the extra aircraft normally goes back to LGW or wherever in sep anyway