Class 450/444

[Phoenix160789]

Please excuse my ignorance, I'm new to this game.

I've seen a lot of screenshots and videos of people using SWT Class 450/444's but for the life of me I can't find any information of what I need to have these.
If anyone can help me, it would be much appreciated.

Thanks!

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BRTrains has a 450 in SWT livery, I am not sure where the 444 is from, as I don't think that does.

edit: it does have the 444.
Do they look like this the ones you've seen? http://imghst.co/98/5tVraysOvW.png (this is the 444 & 450 formed as one train) if they do, its BRTrains - viewtopic.php?f=26&t=74766