Hi this is my first post hoping that someone here has experienced similar and can point me in the tight direction to fix.

I have recently bought a pair of new tyres for my V6 auto mondeo it is on a w plate.
The tyres are a different size to what I started with as apparently the ones I had are incorrect in size, so the 2 new tyres I put on the back as they are bigger and put the ones originally from the back onto the front ( hope this is making sense ) now my TC comes on at 50mph preventing me from going quicker, seems to clear when TC is off but also my ABS now kicks in every time I brake no matter how gentle or hard, all was fine before swapping the wheels round any ideas??