And it’s lights out, and away we go!
Almost all the responses you will get to this question will simply state what the poster owns himself.
The thread will degenerate into an argument between old versus new, big versus small, European versus American. Pretty much every deer legal cartridge south of the .500 Nitro Express will be mentioned and very few sensible reasons will support any of the nominations. One side of the debate will decry the word Creedmoor as if it implies some sort of contagious hard left transgenderism. The other side of the debate will regard anything that has an “x” or “-“ in its name as proof that the poster is an octogenarian antiquarian who attends Boer War reenactments. (Another small group will insist you need a Magnum but you can disregard them as they are unduly influenced by their unfortunately sized appendages.)
All the cartridges mentioned in the thread prior to this post will do the job just nicely, including the .243 you already have. All the cartridges that are yet to be mentioned, but surely will, will also do the job. Being a Yorkshireman, you doubtless have a strong affinity with humble beginnings, child labour in’t pit and proletarian revolution, so I would caution against getting anything too flash. But at the same time you don’t want to encourage the capitalist gentry by getting something classic that suggests you have been reading Country Life. You need something that says Ford Cortina rather than Jaguar XJ12.
Finally may I ask you to please be man enough to actually tell us what you end up buying. 99% of posters of this question, which comes up at least once a week, are scared off by the ensuing venomous argument and we never hear from them again...