BOAC, Greetings from a non-expert...
The rudder spikes may be caused by the yaw damper if the heading is changing rapidly.
Tha left and right aileron positions are sampled once per second, the left on the second, the right on the half-second (approx). If the control wheel is moving rapidly they will show different graph shapes. If you imagine them superimposed it sort of fits!
At 18:18:20 the left engine N1 decreases before the thrust lever is retarded, presumably because of the earth it is ingesting, and who knows what the ailerons will do after that...
Thinking of the broken nosewheel steering cable what we really need is the nosewheel angle - but good old Sod decided that the FDR would not record it!
Not much mention of the surface wind in the docket - surely the microburst capital of the world has very sophisticated wind recorders all over the airfield?