The rudder and aileron aren't locked, it's just a spring-loaded link that takes fairly moderate force to overcome. Somewhere in my manuals I probably have more detail.
They were very low, and the reports' glossing over this puzzles me. They were at about half the typical altitude when they passed the tower. I understand the Electra takes off like a reusable rocket, compared to piston planes of the day. Speaking as a veteran Electra simulator pilot, it was hard to keep the thing low and slow.
I'm confident the CAB was cherry-picking witness statements. At the point where I say the bank started reducing, the CAB concedes that the rate of increase might have briefly stopped. I think that was their concession to voices who they decided to more or less dismiss. In my simulator run I showed what the same flight would have looked like from different viewpoints, and only someone pretty straight-on to the path would have seen the flattening from a distance. No one in the immediate crash area was quoted in the papers.
I don't know how thick the trees were between the RR impact site and the tower. Page 172 shows a clear line between the tower and the and the RR track in the direction of the final wreckage, but I don't know that they could see the RR impact site. My 1960 construction picture
https://ibb.co/krms0w seems to match the ground appearance on page 172, and it shows a block of possible trees just east of the impact site. So the visual contact might have been lost to the tower there.