Counting agents have a number of important roles to play at the count:
they observe the counting process and make sure that it is accurate
they can draw to the attention of count staff any doubtful ballot papers
if they disagree with a decision by the Constituency Returning Officer (CRO) to reject a ballot paper, they can ask the CRO to mark on the ballot paper “rejection objected to”
if a count is suspended for any reason, counting agents can add their seals when the CRO seals the ballot boxes and envelopes
You and your election agent can do anything a counting agent is allowed to do.