At the range I used to be a member of we could use 'hunting ammunition' (soft point) at the range for the purpose of zeroing.
Looking at the Bisley rules they appear to allow 'unlimited' use of plain 'lead'.
Is this diferent to your understanding of the UK situation ?
I think Brian is referring to the time when expanding ammunition was moved to section 5, (only a UK government could be so stupid!) from memory this was rescinded back in 2017?