Trying to sell apartment that is mortgaged

Ive followed a lot of the threads over the years, and it has given me great joy, but never thought i had anything worth contributing.

I have a problem and was hoping someone could come up with a solution.
I am selling my flat in the Marina that has a mortgage on it. I am a UK resident with a Dubai bank account, but i don't have a Dubai check book.

We found a buyer and they backed out because there is a period of time, after they pay my mortgage off and before they get the title deed, and there concern was if I disappeared they would of paid a mortgage off for a property that didn't belong to them, as title would still be mine until transfer.

Now then we have found another buyer, and what the agent is saying is that we have to give a security check, which will be given back to us after the sale, for the value of the loan….But we do not possess a UAE check book, I'm offered to have a lawyer involved to oversee things and they have refused, and it looks as if we are going to lose yet another buyer. Is there anyone that can help me?

Thanks

Frantic