I know plenty of people who live abroad who are English who do manage to get their children to speak English quite well- because English is a very dominant language, they hear it on TV, pop songs, signs, all the time. So, reinforcement is all around them. That won't be the case if you live in the Uk and you want your children to speak, say, Swedish. It does depend a bit on which is the second language, as I say, most of the friends I know that started out speaking their mother tongue (Danish, Swedish, Finnish, French, Dutch) with an English partner haven't got bilingual children now they are older (up to age three they seemed to use both and then English started to dominate when they go to school). Parents where both speak the second language (even if it is not the mother tongue for both) seem to do better.
Starting by speaking OPOL at home is a brilliant basis for bilingualism, but also think how you might be able to reinforce the language and provide opportunities to use it- one great way is long trips home in which the children have to speak the language. I know people who have enrolled their children in the local nursery/summer school for a month when visiting which makes a huge difference as the children have to speak the language (if just on a visit, easy to hang out with the English family and not really speak it). Plus as others have said, music, songs, fun stuff connected with the language help- any grandparents likely to visit and chat to your children? If you are in major cities, there are language clubs and schools for children for different languages- might there be one for your language (or you could even start one with some other parents).
Your husband's reasons for not wanting you to speak your language are just awful though, no-one should tell you which language you should speak to your child, and they are far more likely to end up with a (possibly) accented second language and perfect English given they live in England!