What I like about Google Voice is that I don’t need an additional SIM, it all goes through an app. On iOS it has the VOIP integrations so calls shows up as native calls, text however have to go through their own app. You can receive/make calls/texts for free. Granted, this is Google so they are probably collecting some kind of date. I would love to see someone else to this and I would be happy to pay for it. If there was a provider who could give me the same experience, but also give me a US, UK and a Norwegian number, I would be happy.
According to this article, it should be avaialbe in the UK. However, you can’t have both a UK and a US number, you would need two Google accounts unfortunately.