My document has 3 sections. Sections 1 and 2 are the document (portrait then landscape table). Section 3 is an attachment.

How do I show number of pages for those sections only, e.g. page x of y (y being the total of sections 1 and 2, NOT incl s3?

You have a choice, you can choose to:
1. Hard code the y value or
2. Put a bookmark on the last page of section 2 (ie. where you want the y to get its value from). Then in the footer you replace the y with a crossreference field pointing to that bookmark. The footer fields in sections one and two would then end up something like
Page {Page} of {PageRef BookmarkName}

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Andrew Lockton
Chrysalis Design, Melbourne Australia

Thank you. I did just hardcode the number for the time being, but thought it a good opportunity to find out how to cater for changes to the length of the document.

I tried to follow your advice - I created the bookmark at x but when applied to y it is '1'.

Page Numbering by Greg Maxey