BillFlowerpot I'm not thrilled with the selection on the Currys website, in that there isn't much selection at all. But if you want to keep the price down, this would be fine:
https://www.currys.co.uk/products/msi-mag-infinite-e1-gaming-pc-intel-core-i5-rtx-3050-1-tb-ssd-10275597.html
This is a higher-quality build for £100 more, not better parts (and the processor is weaker but still more than good enough for Sims games), but from a company that does high-end custom builds too. So their standard is higher. On the other hand, you'd have a two-year warranty either way, so maybe it doesn't matter to you.
https://www.currys.co.uk/products/pcspecialist-icon-211-gaming-pc-amd-ryzen-5-rtx-3050-1-tb-ssd-10261457.html
This one is the same as the first except with a much faster graphics card. You don't need it for Sims 3, so it's not worth the money if you're never going to play anything else, but I figured I'd mention it.
https://www.currys.co.uk/products/msi-mag-infinite-s3-gaming-pc-intel-core-i5-rtx-5060-1-tb-ssd-10283888.html
If you have other stores in mind, I'm happy to check those out too. Otherwise, these are your best bets at the moment; the others are from companies that have weak software support or use hard-to-replace parts, or both. But if you don't like these, you could wait a few weeks and ask again. Supply turns over rather quickly in this space, and prices change too.