I have one of those cards too, but manage to spend all the vouchers as I get them somehow.....never sure how that happens!
I don't plan what I need seedwise too carefully as there will always be some temptations I have to make room for somehow...last year it was Sarah Raven flower seeds, I'm still planting stuff out now! I like to try things I haven't grown before, I'm gradually narrowing down my all time favourite list, but tomatoes are my weakness, can't resist a new variety!