Many thanks for the responses. Apologies for my delay in replying – I’m currently posting a LOT of hours at work!

Interesting ideas from both of you – particularly creating a PDF from the Word file and importing that.

I used to import the word document using cmd+D so the basic table structure from Word would stay intact and then restyle it using style sheets in InDesign. Over the past few days I’ve exported the Word file to plain text, imported that and then applied my style sheets. This takes longer to build the table but it does seem more stable, plus I avoild switching from two columns to one column in the same text box – and I’ve yet to format a continuous three-page table, so that may have something to do with it.