these grant work companies are far from organised, there just little companies that land a big contract, need alot of employees in a short time and never build up like they should, believe me ive worked/subbied for most of them, they all like to say how big they are and what there turnover is but when it comes down to it, there shoddy. the work they produce is good overall its just the business side most of them are bad at.
but when i first started doing them years ago i was put on snagging so i was driving about sorting other peoples fail which taught me what the inspectors like to see and what they dont. and never think 'thats the regs so itll be ok' because sometimes there spec is to the regs and more, all TT systems need to have a 10mm earth to gas and water, even though the regs let you get away with 6mm. and was your bath rad bonded? if not that will fail unless you write 'bath rad <0.05 ohms' on the cert.
its plumbers ticking boxes at the end of the day