Where in Hertfordshire are you? I'm in St Neots, just over the Beds border so depending where you are I may be able to do this door fitting. Doors look like standard Howden/B&Q/Wickes hollow panel doors so not a problem, I've done this sort of thing loads of times. I reckon a day and half's work. I'm semi retired so can do it this week if you like. £250 as you've offered.
Colin
07810 481 941
Colin
07810 481 941