@silverwings4 its worth driving 300kms on a week end you can enjoy the long drive too on return with new shoes
whats the point in having two diff size atleast if it was rwd would have some diff in performance and if you have a puncher and need to use the spare wheel will have tough time to drive and also it will reduce the tires life with diff size so all to gether you will be loosing more money than for the fuel for 300kms think it again before changing
or else the best option would be can go with the same size even in the front as you wanted in the back and use spacers to get the wheels out so it doesnt touches the inner arch at corners but it will increase the wideness of your car dimension