Investigators will likely prioritise overseeing the collection of time sensitive data, then anything that would be disturbed by the recovery process. Beyond that time critical task, capacity should only affect timely reporting of findings rather than the quality of an investigation. I have an idea they have a team either end of the country anyway so they may get cover to Essex even if they're still tied up at Lewes.
As pointed out above, Clapham Yard will likely just be a statistic. Doubt if they scrambled the helicopter for Volks either.....