There’s lot of options available, you can find 02, Vodafone, etc and you can also find lebara, giffgaff (use 02 network). I use giffgaff, my brother when in france suggest me use lebara, quit cheap for making call to Indonesia or Malaysia.

First one you need to check is, did it offer unlimited internet? Because nowadays, data connection is more important than sms or voice call. Giffgaff offer £12 monthly with unlimited internet.

If you still use or origin Indonesia number, you need to check which one the roaming partners for your provider. I use XL which partner with vodafone (in case you need to check message).

Some case network connection not establish automatic, when in Malaysia they give you auto response, but for simcard from Indonesia you need to select manually your network provider, my wife use malaysia sim card, it auto connect.

And last, thetering issue is not like in Indonesia, this giffgaff or some provider limit the thetering with just 1 device, or you will blocked for 30 minutes.