A lot of council staff too. Election administration is a local government responsibility in Great Britain, and so many councils use their own staff as well as temporary workers. When I worked for Darlington council there was an all-staff email sent before the elections inviting us to sign on for an extra shift of counting for a modest-but-reasonable amount of extra pay.

Quite often in the UK Civil servants do this as in the past there was an assumption that you did not vote.

There are some very strict rules nothing with the candidates name or party name within a certain radius of the poling station - poll watchers cannot go inside the building unless escorted and so on.

Sunderland South is the constituency that usually gets it done first.

They also make sure the roads are clear on the night between the polling stations and the place where the votes get counted.