There are some more informal ways to say welcome in British English, depending on the context:
* Right you are! (This is a bit more friendly and informal.)
* Come in! (Used when someone is entering a room or building)
* Make yourself at home! (Used when someone is visiting your house or a place you're hosting)
* Cheers! (A very casual greeting, often used when someone arrives at a pub or social gathering)
* Good to see you! (Used when you're happy to see someone)
Let me know if you have any other questions!