AFAICS, if one used the OSG's diversity guidance, that would actually make the OPs situation appreciably worse. Admittedly it allows one to apply a diversity of 66% to to the 'total current demand', but it also defines 'total current demand' for a lighting circuit as "Current equivalent to connected load, with a minimum of 100W per lampholder. For the OP's 31 lamps, that would be 3100W - which, after 'diversity' amounts to some 8.9A (assuming 230V).
I know - which is why I was suggesting that he should perhaps now 'reconsider' that approach, rather than get bogged down with all these discussions about current 'ratings' in relation to a very-expensive-to-run installation.
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