Well we better get out of the EU
We’re very likely going to follow the EU policy in my opinion.
Lead is considered a “Severely hazardous substance” and is on the list of Restriction of Hazardous Subsistence, the content of lead (pb) permissible in homogenous materials in CE marked products is limited to 0.1% by weight. Some materials/producer exempt (until July 2021) eg brass having ~3.5% pb
The proposed UKCA mark will be applied to products sold in the UK and will follow the existing and proposed EU regulations. The CE mark will still apply to products sold in the EU.
Whilst the shooting market is significant in the UK, the collective size of the European market would mean cartridge manufacturers either make a UK specific product and a EU product, or more likely in my opinion, will for economic reasons if not otherwise for legislative reasons, phase out lead (and plastics) from their product line up. The USA may be the saving grace here.
By my estimations UK cartridges manufactures generate revenues of about £52M a year, split £18M Gamebore, £18M Hull, £8M Eley Hawk, £8M Lyalvale Express that’s too small a market for fragmenting the product line up. If lead is forced out of the market with legislation, then lead will be more costly to produce, even though the raw material might fall in price a little. Higher priced lead and cheaper priced steel, market forces will probably determine the adoption rate until it’s abandoned altogether and the laggards catch up.
Anyway, that’s my guess for what it’s worth