GETTING RID OF RED! Help please

Semipermanent should not be permanant, so you really should not have to bleach that out to get rid of it.  You should be able to remove it using a product like colorfix, or maybe even hurry it along a great deal with a stripping shampoo.  (Some stripping shampoos are these:  Dawn dish liquid; any shampoo mixed half and half with baking soda; any shampoo that calls itself "clarifying").  One of these, or a combination, will likely get you back to orange and bleached, or way closer to it.  You will need to condition REALLY well after using these, they dry your hair out big time.  You may want to buy a heavy conditioner treatment at your beauty supply shop, or do a mayonnaise treatment after using these, and before you go to light blonde.

If you go for the colorfix, (which works with a little peroxide), make sure to rinse it out REALLY well - it shrinks the molecules in the dye and opens the hair shaft, but it won't remove the color alone, the rinsing action does that.

Your hair may come out a funky unnatural color after this, but it should be closer to the range of the orangy blonde and light blonde you had bleached it to before.  If some of it is still very orangy, you may want to lighten up only those parts with bleach before doing the platinum color.  Please test strand!