If everyone is timed by the same person the error margin should be pretty similar. Whereas a failure of the electronic timing might mean DNF (unless there's human backup) rather than minute error in time. Just make sure you win by minutes rather than seconds if it bothers you..
Yes, that would be impossible at hillingdon manually.
I do wonder about the margins of error though. When events come down to seconds.
Expense is a good point, hence just referencing to national. Would be good to see something coming in, electronic time keeping wise.