Good idea! Much cheaper and more practical. I cannot see the point of blazers, certainly in this part of the world where it is cold and wet for a lot of the time. My DC and DCG didn't/don't have blazers as part of their uniforms, and one family had very good waterproof jackets in the school colour (maroon, so not as easily accessible from chain stores as blue or black) as an optional part of their primary school uniform.
The other point, IMO, about a jumper and polo shirt uniform as opposed to a shirt and tie one is that the children look much neater, whether primary or secondary. No ties with the knot at the second shirt button level and no busty girls embarrassed (or not!) about bursting out of their shirts. Our DC had that kind of uniform and I thought that their school looked much smarter than schools in neighbouring towns where the traditional uniform was in force.