ZSLHF - one small note of caution. A while back a BA a/c (Airbus I think) had a minor 'runway excursion' after landing on a slippery runway. It was put down to the stowing of the speedbrake at too high a speed causing loss of braking effort. Now, I do not know which speed it was, nor any more than that, but a warning was issued that the s/brake should not be stowed before vacating the runway. It was judged that the loss of weight on wheels, even at a lowish speed, was contributory. I would certainly raise a 'grump' if my F/O stowed the speedbrake without checking with me first.