Most of the concrete is dead level, just a few nicks up to 2mm or so, but there is an area where an old wall came out that needs levelling. Floor is dry, but concrete is probably 100 years old, so I doubt there is any kind of membrane -- that means latex-based leveller, doesn't it? Easiest one for me to get is Norcros Pro 50, but I don't think that's appropriate for this... Any recommendations on what's easiest to use and will do the job?