Very glad to hear that no serious accident resulted.
As for a 737 nearly landing on top of a Piper Cherokee, I had a similar thing happen to myself in the United States once. In 1997, bright sunny day at Port Columbus International (CMH) I was in a Cessna 152. I was about to depart on Runway 10R and told to 'taxi into position and hold', which I did. I sat there, patiently waiting for my takeoff clearance for about 8 minutes. The 727 that had landed ahead of me had long since cleared the 'active'. Since I heard nothing, I called the tower asking them when I was going to be given permission to leave this airport. 5 seconds later a very panicky voice come over the radio '£$*&@!^& Cessna 53398, cleared for immediate!! takeoff, Rwy 10R there's a 737 behind you!!!!!' That *sswipe in the tower had forgotten about me!
I firewalled the throttle (inasmuch that is posible in a C-152) and climbed as fast as I could. When I made my right turn to exit the pattern I could see the 737 already turning off onto the taxiway heading toward the gates!!
It's interesting, at that time a lot of my pilot friends were reporting a string of hairy incidents at CMH. I don't know where they got their controllers from at the time. Another one that sticks out is the tower asking me to follow a taxiing United 727 from about 150 ft behind it!! Yeah right!!! Ever heard of jet-blast?? Oh well. I hope they've done something about it.