JustaFew.. I was there (a they say!) and don't recall any thing of a serious trial. I think one or two BA aircraft were fitted and there were procedures laid down but I don't racall ever seeing an MLS approach. Wasn't the whole shooting match abandoned?
Big problem with such things at a major airport is integrating with the "normal" procedures - like the cock-up of the Concorde "Standard Approach", for which a BA F/O made a lot of lolly. But the crews soon realised that a radar approach was the best option - and presumably pilots of other aircraft felt the same.