Hi Sweetie,
First congratulations! Babies are wonderful!
Here is my advice as a child of divorce. Do not get married and do not move to the UK. If you don't love him and you don't think you'll be happy don't do it. You'll just get more misery than you, he or the new baby deserve. I think children would rather have 2 happy parents a part than 2 miserable parents together.
When the baby comes you will need the love and support of your family and friends.
I moved from California to Massachusetts and I am 3500 miles away from my support system and have had 2 lovely boys. It's been harder than it ever had to be if we had stayed where I grew up. But this was a better place for my husband to earn $$$$. I have made friends, but its not the same as having my family.
You need people who will come running at the drop of a hat when you need them.
Also, go to an Attorney now. This guy is being nice now...but what about when you don't do what he wants. Get a child support order and his paternity established. Start thinking about if you want him with you when you have the baby. Start thinking about how you will feel when he takes your child off to the UK without you for visitation. Also you may want to make sure your company has no morals clauses. Here in Massachusetts they have been firing unmarried men and women when they or their spouses get pregnant, because the person signed a morals clause. Go to an Attorney.
Best of luck to you. Big hugs,
Chrystal