Sorry, should have been clearer, the XML is in the form...

<ROOT>
<MEMBER>....</MEMBER>
<MEMBER>....</MEMBER>
<ACCOUNT>...</ACCOUNT>
<ACCOUNT>...</ACCOUNT>
<ACCOUNT>...</ACCOUNT>
</ROOT>
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ie the whole file is (at this time) simply made up of MEMBER and ACCOUNT elements. MEMBER records are processed by one routine, ACCOUNT records are processed by a separate routine.
(I probably don't need twig_roots at this stage, but I've set it up for future use when the file will contain loads of other elements and then I can use it to reduce the overall load on the system)
Thanks