RSS Feed: Neil Blumfield has kindly set up an RSS feed based on this site, the URL for which is http://feed43.com/british-rpg-convention-list.xml. I should say that I've not tried this out myself, especially since this page changed its URL.
Calendar File Form: Roger Bell West has set up a site which converts this page to standard calendar file format, and updates that file periodically. See http://firedrake.org/infobot/ics/conventions.ics for this. Or - I'm told that by using webcal://firedrake.org/infobot/ics/conventions.ics instead, you should be able to "subscribe" to this calendar. Again, I haven't looked at this since this page changed URL.
14th-16th April: Conpulsion 2023, at Teviot Row House, Bristo Square, Edinburgh. As they say, "Conpulsion is Edinburgh's board game and role-playing game convention. It has been running every year since 1987, except 2020 when it was cancelled due to Covid-19 (with the last two years online)." They have an outline programme and are taking game submissions. See https://conpulsion.org/ for more information as things are announced and a contact form, or e-mail them at conpulsion@gmail.com.
2nd-4th June: UK Games Expo 2023, at The NEC Birmingham. Britain's biggest general games convention, with lots of RPG sessions (generally run in the adjacent Hilton hotel) among other features. Prices depends on ages, number of days, etc., and there are several convenient hotels for accommodation (though those fill up quite fast). Just a preliminary date announcement so far, but doubtless more will follow; watch https://www.ukgamesexpo.co.uk/ for details as they're announced.
7th-9th July: Summer Stabcon 2023, at The Guildhall, 169 -171 Wellington Rd South, Stockport, SK1 3UA. A long-running, informal tabletop games convention, which always features some roleplaying. As it is no longer residential, members have to sort out their own accommodation. ("There are several hotels in the area plus various AirBnBs and other options.") Full weekend membership is £15 before May 31, £17.50 after; single-day membership is £7.50 before May 31, £8.75 after. Contact bookings@stabcon.org.uk for a membership form.
26th-27th August: ShadowCon UK 2023, at Northfields Community Centre, Northfields, London, W13 9SS. Assorted RPGs are promised. For more details, see http://www.shadowwarriors.co.uk/; sign-up is supposed to be via Warhorn at https://warhorn.net/events/shadowcon-uk-2023, but that wasn't working when last I tried it.
2nd December: Dragonmeet 2023.Very little information available on this as yet - not even a venue, though it's guaranteed to be in London. The Web site is currently rather confused, with information relating to last year's event, but you can buy tickets from https://www.tickettailor.com/events/dragonmeet.