I think I'd be going for the Gold amex credit card for a year, which is 1 MR point (=1 avios) per £ of spend plus I think 4 Priority Pass lounge entries. Then dump it after 11 months before it starts charging and drop back to what you have. It really depends on your attitude to faffing around for points, but it's not a massive hassle to get one and you might as well earn more.