I use this adhesive all the time for walls.....highly recommended..

Look Here>>>>> Mapei Adesilex P9 adhesive for 'superfix' solution: News from Mapei UK for more info..

Is that the one that comes in a 22kg bag?

20 kg bags and smaller if needed.......
Cement based adhesive with good initial adhesion strength and no vertical slip for ceramic tiles.
Applications:
Interior and exterior bonding of ceramic tiles and mosaics of every type on floors, walls and ceilings on conventional substrates (cement renders and screeds, underfloor heating installations, brick walls, blocks walls, gypsum boards).
Also suitable for tile on tile with medium-size tiles (up to 900 cm2) and spot-bonding of insulating materials such as expanded polystyrene, expanded polyurethane, rock and glass wool, Eraclit® (wood-cement panels), sound-deadening panels, etc.
Installation over gypsum based or anhydrite based surfaces is possible after having first applied Primer G, Mapeprim SP or Primer S. Coverage
2-5 kg/m2. Packaging
20 kg bags, 4x5 kg boxes.

That can't be the stuff then. This bloke was telling me it new for them from Mapei.
Same as keraquick but strictly a 1 part flexi - you can't use the latex solution, and it comes in 22kg bags and the price sounds amazing.

Was it the Ultra flex...? it comes in standard set or fast set and is a single part S2 adhesive..

Could be, not sure. His price for the keraquick was amazing and when he told me the price he'd do me for this stuff at 22kg a go sounds fantastic.

AFAIK, Mapei's single-part S2 adhesive is Ultraflex.