I have listened to the original LiveATC archive (Dec 24, 1100-1130) in real time and have written out the timeline of comments below as they occur in the clip (min:sec). Note the almost 1.5 minutes between his first "Standby" and the controller's asking if he was ready. We missed the initial comment that promted this first "standby", but I wonder if it was the controller asking if he was ready. We may never know.
Look also at the 45 seconds that elapse between his saying he is fully ready and lines up on 28 and the next time he says he's "fully ready...but not finished the checklists". Almost 4 minutes pass before he finally ready to take off. In what country would that be deemed acceptable?
04:00 BA: "Standby"
...
05:22 ATC: "Speedbird845 there's traffic behind you waiting to depart, if you're not ready I'm going to bring you onto the runway to vacate off 34"
05:29 BA: Says they're waiting for the cabin to be ready, it takes about 2 minutes...
05:37 ATC: Orders him to enter 28 and turn off onto 34.
05:42 BA: "Standby"
05:48 ATC: Orders him again onto 28 and off onto 34, traffic behind waiting to depart.
05:54 BA: "Yeah, we just got a phonecall, standby".
...
06:05 BA: "We are fully ready"
06:08 ATC: "Line up 28 and wait"
06:11 BA: "Line up 28 and wait".
06:14 ATC: "And for future reference, etc. etc...."
06:28 BA: "Standby"
...
06:48 ATC: "Speedbird845, are you fully ready?"
06:50 BA: "Affirm...we are just doing the checks as you keep talking over us".
06:55 ATC: "OK, negative, turn right please onto runway 34, that's the 3rd time I've asked you to vacate onto R34. If you're not ready turn onto R34"
07:03 BA: "Madam we are fully ready, we're just trying to complete the checklists but you keep on interrupting us. Standby".
07:09 ATC: Negative, turn right onto 34, I've asked you three times now...."
...
other transmissions...
...
07:34 ATC: "...except when I instruct you THREE times to vacate because there is traffic behind you".
07:40 BA: "What would you like us to do now Madam?"
07:43 ATC: "As I said I will let you depart..." and clears him for takeoff