I think you’ll find that every RM VOC that has the 16’2" trailers - are looking for more candidates to drive the long way around on routes that the full time staff cannot do - due to the “10 hours on duty at night” rule that only applies to Full Timers, rather than Agency who can do 3x15 hours plus 3x13 hour shifts in the same week.
Dodgy bits I recall from where I used to work were (and still are…) “Getting your combination to ELDC Thurrock from kent when the right hand bore of the dartford tunnel seems to be shut every night without fail” and “Accidentally missing the eastbound offslip for hangar lane on the A40…” Where there is a 16’ headroom underpass on the A40 right after that offslip! 
If a shift is likely to be longer than 10 hours on duty at night time - the shift will need to be given out to agency. The full timers cannot pick it up on docket. 