... Yes i had front pads fitted to the rear brakes!
I don't know what you had in the rear but it was not Murena front pads David. They simply won't fit. They would foul the hub before you could get them anywhere near fitting in the caliper.
So my question is .... As my rear pads are used and im not sure used. Are rear pads thinner than fronts?
When new the front and rear pads are the same thickness 14 or 15 mm (can't remember which at this moment). If you fit part worn pads to the rear, then the piston self adjuster needs to be reset. This takes up the free play as the pad wears. All you need to do is make sure the handbrake is fully off so that the levers are fully back, then pump on the brake pedal hard. This will bring the pistons out until the pads are tight on the disc and the mechanism should self adjust. (this mechanism is inside the piston and has to rotate around the centre pin, and it should have a non return ratchet so that when it has rotated it cannot go back). When you release the pedal, the piston now can only release a tiny amount and the system is adjusted.
As this seemed the case. Im gonna have to bleed the brakes and reset the calipers as the rear ones are banging AGAIN as im guessing the caliper is used to a fatter set of pads and are allowing the pad to move as a result.
You don't have to bleed the brakes at all. As you should see from the description above, the self adjusting mechanism has nothing to do with the fluid system. Did you fit the pad anti-rattle springs correctly? Were they holding the pads tight in the forward direction? (rear springs go on the bottom, front springs go at the top).
Roy