Common alternatives for Irish Amazon are German Amazon, which tends to have a better selection and pricing. There's also Caseking in Germany, a dedicated PC parts site that ships to Ireland. In the UK there's Overclockers, which is the sister company of Caseking. Overclockers remove UK VAT and deal in Irish Vat when you select shipping to Ireland, so there's no import fees on delivery. Scan.co.uk is another site that deals in Irish VAT the same way as Overclockers. They are also a PC parts site.

For your build, the main things I'd focus on are the PSU and Motherboard. It's generally not wise to skimp on the PSU, as literally everything relies on it. If a PSU fails, it can take more expensive parts with it. So a better quality one would be best.

You could go with an Arc B580 GPU, which is still great for 1080p gaming and has 12 GB VRAM, which will help for 1440p as well.

For the motherboard, a board with a stronger VRM design and heatsinks will provide better power stability, and suit potential CPU upgrades in the future better as a result.

I'll link a sample build here on German pcpartpicker with parts from Amazon Germany and Caseking. Feel free to change it around. It's around €1300, but that's also with double the RAM, so 32GB would give you much more for multitasking. But you can change it back to 16GB to knock a chunk off the cost.

https://de.pcpartpicker.com/list/rrfsZQ

You can shop around on the other sites as well, you might find some deals going on.

Hope it helps :)