@Beetolicious2 To be honest, I didn't do a totally thorough search, because after checking a few sites, I found one that delivers to Ireland for £10 extra, at least according to the price in the basket, and has a great option for £630, which google says is currently €703. You should double-check, but the website itself also confirms delivery to Ireland in a FAQ.
This desktop has the same processor, graphics card, and memory as the Acer you found. Plus its solid state drive is twice the size of the Acer's, which for practical purposes means you'd have room to install Sims 4 on the SSD and likely keep your user data (saves, saved builds and households, mods and custom content) on that drive as well, instead of having to move everything to the larger, slower mechanical drive. It also somehow has a three year warranty, which is impressive.
https://www.box.co.uk/Cube-Type-Sparrow_2567923.html?config=2335908,2464097,2472017,2482818,2567905
If you want to save a bit of money, this is the same computer, except for a weaker processor. Personally, I'd spend the extra for the stronger CPU for the sake of futureproofing the system in general, but it shouldn't ever make a difference to Sims 4.
https://www.box.co.uk/Cube-Sidewinder_2803928.html?config=2335908,2472017,2567905,2725846,2777615
Both of these systems can be customized, but I'm referring to the default configurations.
For monitors, you can get a very good quality image for well under €200. From the same site, here are three viable options for a 21/22" monitor, from £85 to £95 (€95 to €106):
https://www.box.co.uk/LG-22MK400H-B-22-Full-HD-IPS-FreeSync-7_2401606.html
https://www.box.co.uk/Dell-SE2219H-21.5-Full-HD-IPS-Monitor_2419355.html
https://www.box.co.uk/AOC-22B1HS-21.5-Full-HD-IPS-Monitor_2347140.html
They're all IPS monitors, which is the highest quality category of panel, with the richest colors and the widest viewing angles. The LG monitor has a slightly higher refresh rate, which makes a difference to some people but not others. AOC makes panels for mainstream manufacturers, so even though it's not really a known quantity on its own, its products are comparable to other well-known brands.
These monitors are 24" and all have a 75 Hz refresh rate, and they're only a bit more expensive: £105 to £110.
https://www.box.co.uk/LG-24MK430H-B-24-Full-HD-IPS-FreeSync-7_2401615.html
https://www.box.co.uk/Acer-SA240Y-24-Full-HD-IPS-FreeSync-75H_2569867.html
https://www.box.co.uk/Asus-VZ249HE-23.8-Full-HD-IPS-75Hz-Moni_2139780.html
Samsung calls its IPS monitors PLS, but the concept is the same.
https://www.box.co.uk/Samsung-S24F350H-24-Full-HD-PLS-FreeSyn_1916806.html
I can check other sites as well, but it would be easier if I knew more specifically what you were looking for, so hopefully these options will at least give you a better idea. The one thing you might not want to pay for is a higher resolution monitor: QHD (2560x1440) panels start at almost £200. Still, if you want to see some options, I can look for those too.
If you have more questions, please feel free to ask.
