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. Note that I haven't looked at this since this page changed URL.
2nd December: Dragonmeet 2023, at the Novotel Hammersmith, London, W6 8DR. Britain's primary convention dedicated to RPGs, which has now been running for decades; features will include a trade hall (promised to be bigger than ever this year), game sessions, panels, book signings, an art show, bring & buy, cosplay events, and so on. See the Web site at https://www.dragonmeet.co.uk/ for details, and you can buy tickets from https://www.tickettailor.com/events/dragonmeet.
5th-7th January: Stabcon 2024, 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 £17.50 before Nov 30, £20 after; single-day membership is £8.75 before Nov 30, £10 after. Contact bookings@stabcon.org.uk for a membership form.
30th-31st March: Conpulsion 2024, at The Pleasance, Edinburgh, EH8 9TJ. A well-established university-based convention; just the date and location announced so far. Watch https://conpulsion.org/ for more details as they're announced.
31st May-2nd June: UK Games Expo 2024, 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 aside from the Hilton, there are several convenient hotels for accommodation (though those fill up quite fast). Just a preliminary date announcement so far ("Trade enquiries from October 2023, Ticket sales live from December 2023"), but early e-mail enquiries can apparently go to richard@ukgamesexpo.co.uk; watch https://www.ukgamesexpo.co.uk/ for more details as they're announced.
26th-29th July: Continuum 2024, at Cranfield University CMDC, Wharley End, Cranfield, MK43 0AW. (Note: this location has changed due to an unexpected cancellation by the usual venue.) This long-running, previously biannual convention has now gone annual. So far,just the dates and venue have been announced for 2024; "Registrations will open Early 2024.". Watch https://continuumconvention.co.uk/ for more information.