I did this exact routing last year. The BA flight was 45 minutes late and I missed the Malaysian service as the bags were also delayed coming out.

Soon rectified by buying an Air Asia flight out to HKT a few hours later for minimal cost which I then claimed back on travel insurance.

Without bags it would have been tight but doable. If we'd been any more than 45 mins delayed, it wouldn't have worked.

Of course if the OW alliance still through-checked to all partner airlines, on separate tickets, this wouldn't have happened. Happily on the return, Malaysian sent the bags all the way to LHR from HKT via themselves and BA. I had booked two singles with MH so as to protect the return.