HA brake hangs despite new coverings and discs

Hi, for my Mini Cooper (r50) have got new discs and pads in the back. Unfortunately, the brake hangs easily now, when driving you don’t notice it, but the brake is getting very hot and then you notice on the bus that it grinds. However, the brake calipers are free and do not hang. Now the mechanic said that it is either on the hand brake (which, however, is quite normal: 4 points to fixed) or is on the brake hoses (in the 10 year old car already over??) . If then imemr n Is that all right, or are there other sources of error and or test that I could do? mfg Imsi