Brake imbalance, ABS light on.

[Mighty306]

As Johnny said previously, if you need to / choose to remove callipers when replacing your rear beam, be prepared to replace some of the hard brake lines as well.  The nuts & the lines fuse themselves together so when you undo the nut it twists & damages the line (to a compromising degree).  I've had to teach myself to make up new lines from cupro-nickel pipe - not too difficult & can direct you to decent tools & resources if you need.

If on closer inspection you decide the rear callipers are shot they still seem to be readily available & only about £40 each.