Conor, what you did not get during the five year voluntary transition was the support of the cartridge manufacturers and importers, possibly because you did not engage with them prior to the announcement.
What you needed was for them to totally stop making and selling lead shot cartridges in shot sizes bigger than u.k. 7.5, 2.3mm. Thus making for all but a few, all live quarry cartridges non toxic and yes with single use plastic wads until they could be replaced with biodegradable wads.
But that would probably have been financial suicide for the them to have done so, so now to bring an end to all the negative publicity of using lead shot a legal ban is seen as necessary. including clay shooting, which even the scientists are not calling for, but the HSE has concluded we cannot be trusted if lead shot continues to be sold.