Just to close this thread off, here’s how it ended.
I went to the Liverpool passport office yesterday, I arrived at 8am and joined a queue of about 30 people. I queued outside for 7 and a half hours and got inside at 15:30 and waited for another hour to be seen. I was told my sons passport was being dealt with by Southport office. The lady phoned through to Southport and confirmed it would be dealt with today and to wait for a phone call to collect.
I got a text this morning to say the passport had been processed and approved. I then left for the Liverpool passport office, this is we’re things got interesting.
When I got to the front of the queue the lady told me that the passport had been printed in their central printing location and sent for posting! At this point I was broken. She suggested I do a whole new paper application and get new passport photo’s printed. Luckily I had a photo on my phone and went to get it printed. Amazingly they processed this application in two hours and I NOW HAVE THE PASSPORT and we fly on Monday!!!