Tiling onto old wall - prep?

[SuperPav]

Could the experts here recommend how to prepare this wall for tiling (porcelain 10mm tiles, nothing mental)...

 

It's old paint over plaster, on a cement scratch coat (i.e. it's like external render underneath, rather than loose plaster). It's very hard to chip off from the underlying brick/block and is very solid, so it's definitely not coming off (tried that in one of the other rooms already). The skim has some cracks but is otherwise sound ant not hollow anywhere, and I've had a go with the scraper to get the worst layers of lining paper/paint off and it looks like the photo below.

 

This is going to be a downstairs bathroom (with some of the wall inside the shower) that is VERY tight on width, so I'd like to keep the build up as small as possible...

 

Options:

1) Fill the few "big" holes e.g. where a backbox was, then coat the whole thing as is with a tanking coat, and tile straight on - best for thickness!

2) Glue 6mm backerboard with mechanical fixings into the brick, tile on that. Half way house.

3) Stick no more ply or STS backer board with tile adhesive + mechanical fixings,  then tile on that. The worry with this is it's adding a further 15mm build up in adhesive and board that I really would prefer to avoid in a 1000mm space...

 

 

 

[nod]

Put a wire brush attachment in you drill Get all the yellow stuff off then paint with SBR mixed 3-1 

Your good to go 

[SuperPav]

Thanks nod! As it'll be a tanked room, presumably instead of SBR, just use paint-on-tanking? 

 

Or alternatively is there something like Everbuild 507 (effectively a waterproof blue grit as far as i can see) which will do both jobs?