Is Orange part of T Mobile or are they seperate companies?

They are both part of the same company - Everything Everywhere.

They are both part of the same company called Everything Everywhere but the brands are still separate, so you can still get a phone with either Orange or T-Mobile

Thanks.

Also... don't panic if your T-mobile phone sometimes says Orange-Tmobile on it, it's because they share networks when you have no "own network" coverage.

and vice versa. Im on orange and occasionally it says Orange-T mobile.