I also wondered about this whole plan between them thing but think it's unlikely for a few reasons:
-My ex introduced me to his whole family, like 100s of them when I went there at Christmas. He went out of his way to introduce me to everyone. I don't think he'd have done that if he really thought it wouldn't work out as it made things awkward for him afterwards.
-I think if she's really that jealous she wouldn't have let him go off with someone else.
Yes, it's very possible she wasn't in on it, as it were.
It sounds more like, with a background of desperation to emigrate, he made plans with you and was willing to TTC with you. He probably saw you had a decent job, were well set up, had a supportive family etc.
It looks like something changed about his desire to settle in the UK though -he probably saw it would be difficult for him/his prospects weren't great/weather shit/expensive/language barrier/culturally not for him/far from Colombia/who knows (?)
And alongside that perhaps she let him know of her plans to sell/wrap up her business and move to the US, with family (already established there) willing to support her. It was probably a more desirable prospect - lots of Colombians, can get away with speaking/writing Spanish (I saw a documentary recently where the makers went to a Southern state and literally couldn't find anyone who spoke English when making enquiries), better climate, close to Colombia etc etc
He decided he was going for that setup and abandoned his plans with you. Even with you pregnant, he ok'd that with himself. He doesn't strike me as a man who was very emotionally involved or invested, no matter what he was saying
What you heard about his reputation and behaviour in relationships/towards women seems to corroborate that.
As I said he could be staying in the minimum (and inappropriate) contact he's in due to any combo of back up plan, guilt, pressure from family, image etc.
I think they he stayed in contact with her pretty much all along though.