Ownership of property in Nigeria?

I recommend you not bash your head against a brick wall. Whether your 'ex partner' owns property in Nigeria or not is not going to be of any value to you as there will be no way that you can claim anything as a foreigner in the most corrupt country in the world.

But if bashing your head against brick walls is your thing, subpoena his UK bank records. These will show a paper trail into or out of Nigeria if he has an account there. If he owns property he must have a local bank account. Once you find a transfer, you can get the wire transfer record which will have the account number and bank on it. You might even be able to access the Nigerian bank account records if you pay a large enough bribe and from this you will be able to see if he is paying things like an electric bill. At that point, however, your trail will go cold.

EDIT: I see from your other question that you are actually trying to find out if he is hiding income rather than trying to get hold of property. That is much easier to trace as you cannot move cash across borders, even Belgian dentists with big car boots have trouble doing that. He must be depositing the money into an account in the UK and then transferring it. You just need to find the account.

Are you a US citizen? If so, maybe you can contact the US Embassy there and see if they can help?