recently had my ABS and ESC warning light on my dash has turned on: 

I have used a reader to find the code but no code is being shown, so I checked brake fluid levels, they are optimal, I then changed brake pad (needed to change anyway) however still hasn't turned the warning lights off.

so I then changed the ABS sensors on the front L and R of the car, both of which didn't turn the warning lights off

 

could it possibly be the rear ABS (even though no code is being shown?) , at this stage completely lost on what could be wrong and need doing. any help would be appreciated 

Did you use a system like VCDS or just a standard OBDII reader? An OBDII reader will not pick up ABS faults.