I did one years ago, worked OK, at least we didn't get any damp.

Its effectiveness does depend on the wall construction and the type of brick, some bricks won't take up the fluid so well.

I'd consider doing it for myself again but I wouldn't do it for anyone else, it's a specialist job really, especially if you are going to give a guarantee.

I just went to a hire centre and hired the compressor and bought a big drum of treatment from them

I had my walls done by Mercian and they used a waxy type substance rather than liquid - which to my simple brain will just run away to nowhere. The initial injection only managed to make it as far as the inner wall and didn't actually get to the external wall and so after we'd painted outside, damp started to come through.

I always judge a company on how they react to a problem and Mercian were tops. They came out and did the external wall foc (I paid for the material which would have got used in the first place) and the damp has gone.