The expenses incurred by the clerk on behalf of the council are part of the council's accounting documents. LGA 1972 228 (3) states that the accounts of a local authority and of any proper office of a local authority shall be open to the inspection of any member of the authority, and any such member may make a copy of or extract from the accounts.
So it seems that you have every right to the information, and there is no good reason for the clerk not to provide it in a timely fashion. The clerk should regard oversight by councillors in a more positive light. Lack of care can lead to disaster - occasionally clerks are prosecuted for stealing council funds and it is no service to a clerk to put temptation in their way. Nobody should regard sensible audit provisions as anything but precautionary - there is no implication of dishonesty at all.
It is, of course, best if there can be a constructive relationship between clerk and councillors.