Hi Michael,
I can't help you with the main thrust of your query as I don't know if the Central Bank guidelines for lenders are published anywhere.
But I do know that the guidelines are only intended to guide how much a lender should extend as a maximum to an applicant. As far as I know the Central Bank does not stipulate that any lender should lend up to a recommended amount for any given applicant.
To put it another way, if a lender decides for its own reasons to use absurdly conservative lending criteria, I don't think the Central Bank would have an issue.