Without a pic its a bit hit and miss,but maybe just pull the old plugs out of the wall assuming there are plugs and it was not just screwed into plaster,then hammer in a couple of oversized wooden dowels and screw into those.
Don't know the rules and regs but I have always used full bed on walls and floors, those are fairly hefty lumps so i reckon full bed and you should be stuck for life :)
Have used One Shot before and it worked well but that was on a blocked shower drain,i don't think it is for large bore pipework like you get in a manhole.
This may be of interest and save you a few quid ,Ebay have offers on a pretty good selection of tools and accessories till 11th August ,savings of 50% and in some cases a lot more than that can be found on a wide range of goodies.
Fixed the loo seat when the little pads on the underside wore out ,overfilled the recess with hmg and trimmed to size when set,worked perfectly and has lasted for a couple of years so far:)
Phone them again (hopefully you will speak to another person) and tell them you are not happy with the service provided and you are not in any way- shape or form at fault for them not providing the correct instructions for your purchase,forcing you to visit their website to get the required...
Colour is a personal thing really so whatever floats yer boat, I would not paint the brickwork but i would have some re-pointing done.Just give the steps a good blasting with a power washer.:)