How can we collect magazine subscriptions simply and efficiently?

Our magazine is 60 page A5 page format. We published 12 times a year with 11 paid for issues of 450 and one free distribution of 900 copies. At the end of the year we include a little brown envelope in the magazine inviting renewals and new subscriptions. The envelopes invite people to give their subscription by Gift Aid. Money (currently £5 for the year) is returned to each individual distributor (20 of them), they then hand the money to the 'distributor-in-chief'. They count the money, handing cash to the PCC treasurer and envlopes to the Gift Aid Organiser. This feels complicated to us but we can't think of another way of doing it. Any ideas for a simply, quick, easy and cost efficient system of collecting lmagazine subscriptions? We raised £2800 from subscriptions and donations last year and recovered £600 in Gift Aid.