Right, Charles Lancaster Ltd were taken over by another London Gunmaker called Joseph Lang & Co. (who coincidentally made my grandfather's 12 bore). They no longer trade under that name but as far as I can tell still exist under the name Atkin, Grant & Lang, no longer based in London, but in St Albans, Hertfordshire. I suspect they no longer make guns, just buy and sell old ones. They will trace the provenance of an old gun for £25. Their website, and all further details are

here

I hope this is helpful, it's the best I can do.

Paul