Vauxhall Astra brakes sticking and over heating. changed brake pads, discs, calliper's

Check the pads are sliding freely in callipers and pistons are not seized

Gotta agree. Many Techs don't clean down the calipers and sliders which can get worn or seized. This can and will caused braking system failures.
It's not just a case of " slap in a set of cheap brake pads". The job entails cleaning/lubricating and checking for wear n tear before fitting new brake pads/shoes.

all new. twice and still have the problem

did not have a problem with the brakes until had the pads and disks changed

It could be the brake front flex hose/s collapsed internally and restricting the flow back of fluid which then hold the pads on and causes overheating .

will ask about that, it has 4 fitters stumped at the garage

It is a fault that can happen on all cars and can be caused if brake hoses are clamped to stop fluid leakage when working on or replacing callipers . Even calliper " dropped " and stretching hose can cause it .

Well let you know once i have spoken to them

The brake hoses wouldn’t have been clamped to change the brake pads as the pistons would’ve been pushed back to allow room for the new pads. It’s definitely worth stripping the pads again and working the piston with some duck oil or something similar and pumping it back out (carefully and not too far) and repeating a few times. Copper grease is a good thing to use on the sliders and back of the pads. Hope you get this sorted

Would you please stop replying to old posts already answered !!!

Brake hoses can collapse internally if clamped or not and regularly do .