He told her that i have a boyfriend?

Ask him.

FWB expiry sounds near, start making other arrangements.

What do you mean by this?

because he found someone who's worth being in a relationship with. If things progress between them and they become a couple u can't possibly expect to stay fwb do u?

What do you mean by this?

If you're tossing about the term fwb you should honestly be aware of this?...

It's temporary... if you were going to get closer and make a real go of it you would have by now... so otherwise a FWB lasts until one of you gets too attached to the other... or meets someone they do want a 'real' relationship with, and your 'fwb' will be v quickly kicked into the long grass as far as future goes with the new girl. They may still take sex if it's offered on a plate for now.

But he barely knows her? All he's done is watch her for months end, observe her and spoken to her these days. How does he know what she's worth?

Why say I have a boyfriend when literally telling her that he's going to a female friends house?

To minimise you as competition in their eyes.

Maybe they fancy themselves as a playboy keeping both of you on the boil.

You mean so that she doesn't get jealous???

Broadly, yea.

An old fashioned saying is 'If you love it, put a ring on it', but there's a solid truth there. You can't complain at a fwb leaving for a more solid relationship elsewhere, and a part of that will often involve distancing from their casual past.

He's probably planning to stop hooking up with you if she agrees to dating and sexual activity with him.
There is also a chance that in addition to being deceitful/downright dishonest with her, he might be willing to have sex with each of you behind the other's back and lie through his teeth to avoid either of you catching on to his game.

If you don't currently have a bf and he knows that you don't- do not trust a word that this guy tells you.
You may want to consider finding a new fwb or 'no strings' guy who is more honest.
Personally I wouldn't want to get intimately involved with a guy who is that opportunistic and deceitful.
Good luck!

Broadly, yea.

An old fashioned saying is 'If you love it, put a ring on it', but there's a solid truth there. You can't complain at a fwb leaving for a more solid relationship elsewhere, and a part of that will often involve distancing from their casual past.

He's planned in his head that he wants to stay with her during Christmas and New Year. As he explicitly told me that he's not going to be here for Christmas or New Year.

Time for you to move on and end contact with him.
Plenty more attractive single fish in the dating sea, whether you are looking for another fwb or a relationship.
Good luck!

But she has to agree to him right???