Sounds like the Common Travel Area won't apply to citizens of the EU, EEA or Switzerland, other than Irish citizens. If you hail from anywhere else, and cross the Irish border to work, you'll need a "frontier worker" permit. (See pp.18-19 of HOC briefing.)
researchbriefings.files.parliament.uk/documents/CBP-…
researchbriefings.files.parliament.uk/documents/CBP-…
Also worth noting for EU citizens: it sounds like you lose any accumulated period of residence that counted towards the 5 years you need for settled status if you go to prison for any length of time at all.
Example: live in the UK 4 years 11 months, 1 day in prison, resets to 0.
Example: live in the UK 4 years 11 months, 1 day in prison, resets to 0.
(The only exception to this prison issue is if you already had accumulated a full 5+ continuous years residence prior to being imprisoned.)
