I have started to level the concrete floor using Mapei Self Levelling Compound. I have never used this stuff before and found the mixing of it quite tricky as I needed and extra set of hands. I should have masked off the timber boarding under the mezzanine as using the spiked roller made it spatter everywhere - lesson learnt! I only have three bags and one hasn't covered a third, so I am definitely going to need at least one more.
Update and lessons learnt. ... On the second mix I used a mortar float to spread the mix out better prior to going over it with the spiked roller and it went so much further. I ended up only needing the three bags I had bought.