Your SO 1(a) has given authority to the Mayor (hmm, interesting as this would normally be the chairman of said meeting), alone to change the order of the agenda whereas 10(a) is a standard SO which allows a request to change the order of the agenda to be considered without giving 3 clear days notice of the intention to propose this. They're not exactly in conflict but together the result is a request can be made (without notice) to change the agenda order but authority to make a decision arising from that request being delegated to the Town Mayor who, in your example, refused the request.
Slightly unusual to delegate authority like this to a named person (even if named by virtue of their office) as it begs the question what if the Town Mayor is not chairing the meeting or not in attendance at said meeting?