the reason people dont paint brick is due to the fact is not very porous so the paint does not stick well and usually flakes off.

Main thing to do is to prep it well, power wash then fungicidal solution.

Make sure the brick is totally dry then apply a good primer coat, usually thinned down main coat.

Dont use cheap B&Q products and that included the main brands sold at these places - go to a paint company/ trade outlet and buy direct

Also go for an oil based product rather than water based at this time of year otherwise a shower will wash it all off before it dries.

Best trade product we used to use was Leyland Masonary paint, but Manders, Dulux etc is good. The stuff sold direct is always better than the crap stuff they label up for the stores.

If a surveyor questioned the paint afterwards you can then throw this info at them.