E90 brakes sticking

[mrLEE30]

Mate just got a cheap 325 E90. runs nice but brakes stick, very noticable when reversing, you need to tap the throttle to get it to go, then it binds again when brakes reapplied, if you leave it long enough at idle it suddenly un binds and goes, makes for hard reversing.

I have just changed pads and disks (quite cheap parts..not!), same thing, removed and inspected brake master cylinder and all good here but still same, my next thought is the ABS pump not releasing pressure.

For a giggle i phoned the stealers who told me a new one is about 2k after getting over the shock i am wondering is there is anyhting obvious i forgot, or is there any thing servicable inside the ABS pump?

ABS works fine by the way when driving.

cheers in advance

[mrLEE30]

2007 i think if that makes any difference, pre facelift but with N5x engine