MH do if you phone them. I did two big trips earlier in the year GIB-LHR-BKK-KUL-PEK-LHR/LGW-AGP. I flew BKK-PEK with MH, tried to get BA switch the seats, but there was problems, phoned MH and it was sorted.
I have more problems with IB than MH, but that's another story...
