purple,

100% normal!

You feel how you feel, and you cannot help that. Everybody is different.
I can easily understand that you're having a hard time with this.

Firstly though, purple, you need to recognise your value. You have him now.
You are the most important thing in his life and he travels half way round the world
to see you.

Always remember he chose to marry you because he loves YOU.
This previous relationship didn't work out.
Don't strain your relationship with him by not respecting the life he had before you.
If this ex-g/f or your husband were behaving inappropriately with each other, that would be another story.
But there is no evidence of this.

Trust your husband. Nothing will work in your marraige if you don't trust your husband.
If you do then you can let him be as nice to her as he wants. You know that he's not even thinking about leaving you for her, and you have no logical reason to be jealous.

Having said it's natural to feel threatened by someone your spouse used to be involved with, it's really not fair that you should be so worried about that. Whether she's calling him, visiting him on occasion or just friends with him, the uncomfortable feelings are probably always going to be at the forefront of your mind.
If this is happening to you and you're losing sleep worrying over it,something needs to change.

Not just because you are worried he is doing something with her, or not for any other reason, other than you have told him that it upsets you. That should be enough.
When you are in a relationship, particularly a marriage, and you really respect and love that person, you don't do things that you know upset them.

If you're not OK with it, then it has to be a NO.
If he didnt know it upset you then fine but it seems you have told him, right?

I feel sure that many members here would agree that the last person you would like to bump into is your loved one's ex (ex boyfriend, ex girlfriend, etc.) And the worse is, both you and "the ex" are trapped in the same place. The question is how would you handle the situation?
How would you act and re-act?

I say this purple, because given the information you have shared, it seems that when you are with your husband here in UK, and living together in his house, you will likely see and meet this ex-g/f as she is 'in the area'.

Don't allow your husband's ex girlfriend to threaten your relationship with him.
You are not wrong, but you need to focus your thoughts and energy on your marriage.
Enjoy every moment. You love your husband, and he loves you. It will be an adjustment for everyone, the ex included. Agree to reasonable boundaries with your husband. Be flexible and confident.

Remember time is precious. Don't exhaust your emotions on her!
She is the past and you are his wonderful present and beautiful future.