Had all pads changed and brake pad warning light keeps coming on any ideas why. 

Take it back - pad warning is only on the front pads AFAIK - it could be a cable issue or issue with the new pads.

I believe the warning used to come up if the brake fluid level was low, not sure if it still does or has separate  low level warning now.

There is a separate fluid low warning, it’s likely as above sensor wire not installed or broken.

It’s the driver side front for reference.

Thanks guys for your help going BK to dealers.