We did too. Blazers won by a landslide!
Student thoughts were they look smarter, needed less washing (so would discolour less), and actually worked out cheaper, as most people would just have one. Also bonus of it being an extra layer (as no one wore coats previously over the shirt, tie and jumper previous uniform), and having pockets to carry stuff.
We had a sew on badge, and most of the uniform could come from any supermarket - black blazer, white shirts, back trousers (or skirts, but most didn't wear them, as rules on length, tightness etc was an issue), black smart shoes.
Optional jumper with school logo, mandatory tie and mandatory sew on badge had to be bought from the proper supplier, and the school shop also held some - tie was £5 and badge was £3.
Pe kit was a polo from the school supplier, plus black trackies or joggers, and trainers.
It was costed up before it was brought in, and you could get a years worth of uniform (1 blazer, 2 jumpers, 5 shirts, 2 trousers, tie, pe top, and joggers) for about £100 from most supermarkets. I get this doesn't include bags or shoes, but realistically, nearly every parent would have spent more buying non-uniform stuff.
School uniforms are fab, but need to be implemented sensibly - no excessive amounts of branded and logo'd items, sensible rules for extreme weathers and sports, a bit of chill on exactly how it's worn, and support for those who genuinely need it.