X5 braking issue

[Greeny]

Had the front brakes lock on the car today, all the brake warning lights came on, by the time I pulled, slowly, into somewhere safe, disks were smoking hot!
While waiting for the AA, lights went off and the brakes freed off, and l carefully drove home with the AA man following me. Brakes did not seize on again, but the pedal does not seem right, fine if you stamp on them, but if you push slowly, pedal goes really long, but brakes still work.
Reservoir full, one brake pipe replaced recently.
Any ideas?

[Mr2Mike]

Were all the brakes smoking or just one wheel?

[Greeny]

Both the fronts, the rears not evident.
Since replaced master cylinder, and fixed.