I really thought the idea of UK stock was a bit far fetched. The UK have brought in quite a bit of new stock in the last few years, but most trains being replaced are close to their end of life, and I suspect many would be difficult to make comply with current safety standards. What do we want - Pacers?
The 41 extra coaches are at best a stop gap measure to alleviate the worst overcrowding, but I would expect most of that extra capacity will be immediately filled as soon as they arrive.
I believe there's also a process in place to order up to 600 new DART coaches, which would be a mix of all-electric and bi-mode units (I'm not sure whether a decision has been made on whether they will be diesel-electric or battery-electric yet). I think the earliest these would begin to enter service is around 2024.
It should be noted that the 8100 DART coaches will be 40 years old at this point. They still look good after their mid-life refurb, but part of the new order will probably be replacing them.
This should free up most of the Diesel stock serving the Dublin commuter routes, allowing them to cascade on to other routes.
However a lot of uncomfortable commuters until they arrive, and expect politicians to delay the funding and push things back a few extra years.