That was a real eye opener of a documentary - even the loos and coffee makers are checked!
Adding onto what Darren said, all UK, EU and American registered aircraft (from two seater Cessna's to Airbus 380's) have to adhere to a rigorous maintenance program which is worked out by the aircraft manufacturer and the country aviation authority - in our case the CAA. Every step in that program is documented and has to be double checked and signed off, and any parts (new or used) replaced logged. It doesn't matter that Thomson, EasyJet or whoever are "low cost" airlines - their planes will not fall out of the sky because of lack of maintenance, They choose to do the maintenance at times when it wont not to get in the way of your holiday. These "heavy" maintenance checks are often booked years in advance. There is also a diagnostic check carried out almost every second of every flight on the Thomson (and others) fleet and the engineers will often see a potential fault before the (very highly trained) pilots.