I'm on the way home now, I looked at OPI and CND, everything was regular price. There were some CND packages which work out cheaper than buying everything separately, I think these were the only show deals they had. Moyou London and Roo bags had show deals on most products. There were show deals around but for courses and so such but only if you book there and then.
It's great to walk around, there's loads of demonstrations happening and people to talk to about products and brands you might be interested. However for me it wasn't a shopping day as I would rather order all online and not have to lug it home! Nailympia is going on upstairs, I missed all the competitions so if you're interested in that I would recommend finding out the times before you leave.
Food and drinks were also kinda expensive (London prices)
Hope you have a good time!x