MIG wrote:

I also wonder what happened to anyone's bank balance that ended in ½p.

If half the population's accounts ended in ½p that could be a bit of
extra/loss of money for the banks (about £200 000 between the UK
banks?), whichever way it was rounded, but I bet that hardly anyone
either paid or deposited amounts ending in ½p in banks for a long time
before that.

I'd disagree - a lot of people often put some of their loose change in when
depositing cheques, at least whilst the banks still allow such deposits. The
chances of a spare ½p ending up would have been quite strong.