Took me a long time to settle after living in UK for 10 years. Main things that come to mind, in particular, the public transport system, was used to London buses and tubes were you they arrive every few minutes, enabling you to get from one side of London to the other, unlike in Dublin were it takes a half a day to get anywhere. Was advised by HSE job I would be better off getting a car and would actually earn more money in travelling expenses, in contrast to London where public sector workers travelling to city centre are given financial incentives, ie season ticket, for using public transport and even more for using a bicycle. I therefore reluctantly got a car.
Completely shocked by amount of road users driving with L plates, with no basic concept of rules of road. Road signs where they exist, are confusing, can think of loads of areas in city centre with no clear directions of lane you should be driving in or where exits lead of roundabouts, telepathy is a useful attribute.
Working in the health service was a massive culture shock, partciularly in certain areas which are at least 50 years behind in terms of services and resources for sick and vulnerable people. I was gobssmacked to witness the conditions these people are being 'cared for'. Unbelievable costs of health care, to see a Gp, A&E - all freee on NHS.
Lots of other smaller things are very irritating such as banking, loosing your documents, which in ther UK are just so much more efficient and reliable. Postal service is completely hit or miss, with no Saturday service. Have been p - off at how long it has taken to post a parcel nationally, and this is something other non-Irish people have also experienced. For example,a German friend had a parcel sent from Germany in 3 days, which then took a further 2 weeks to locate from one of the sorting offices. Have found shops rude and unhelpful, partciularly when returning goods, with the insinuation you wore the item of clothing, hundreds of questions about why its being returned, then a snotty refund. In UK, you refunded without any of this nonsense.
If you complain about anything, especially in restaurants,people often become defensive and take it as a personal insult, without apologising.
From talking to many non-Irish people they find the Irish phenomenon of being really friendly and of inviting your trust by making promises or agreement, then never doing it, yet laughing it off as something normal - dont know if anyone knows what I mean...At the risk of completely generalising, I've found English people take a lot longer to get to know someone, either in work or socially, this can often be seen as 'stiff uppper lip', however when they get to know and trust you, its genuine, whereas Irish people - Am going to get killed for this - are very chatty and sociable but sometimes full of complete 'blarney'.
However, after saying that, if you can overcome some of the above, the pros outweigh the negatives...