Sorry, it took me a little while to see this follow up - you could have replied to the earlier thread so that I received a notification.
If he is on a visitor's visa then he has to return home if he is to secure a visa based on your marriage so that you can marry.
Whether you marry over there is a decision for you to make. Marrying in Trinidad would be the cheapest (though you would have to factor in the expense of you traveling there)and require less paperwork because you would only have to make one application (ie. for a spouses visa) and pay one application fee.
If he obtains a fiance visa the you would have to make two applications and pay two fees - one for the fiance visa and a second for the spouse's visa once you have married in the UK.
The criteria for a fiance visa and a spouses visa is very similar and if you are successful in apply for one then you will almost certainly be successful in the other.
The drawback in going for the cheaper/less paperwork option of a spouses visa application following marriage in Trinidad is that if you are not successful then he will be stuck there but you will still be married.
It's for you to decide whether you meet the eligibility criteria, if you are not sure then I would take your details to a local immigration solicitor for his view on our eligibility.
Hope this clarifies.