It's Christmas, so maybe some positive things that expats miss about Ireland to counteract the negativity in the thread about what we DON'T miss.
For me - it's open fires. Londoners don't seem to value open fires in the same way as the Irish, so it's really difficult to find a place with an open fire - even houses that originally had them often have them blocked - and there are few things better than being sat in front of a roaring fire.
Linked to that - and don't tell Ming - is turf. Admittedly more a rural thing than an Irish thing, but the only thing better than being sat in front of a roaring fire is if that fire is a turf fire, with all the smell and memories of hand cut turf.
Then there's the spontanaity that comes with a combination of living in a small town with also being Irish. In London, everyone I know is based all across London so there really is no prospect of people just nipping in for tea, or a few friends dropping by on a friday night convincing you to go to the pub. It's not just being a big city though - I think there's something uniquely Irish about dropping in to someone unannounced or uninvited for a cup of tea and letting the evening take you where it takes you.
And of course - taytos, cidona and club orange...