Better than applying silicone, which as Canardly so correctly says can result in spalled brickwork if moisture does get into the brick and freezes, is a newer product called Stormdry, which is slopped onto the wall and soaks in far more than the silicone or Thompson's water seal sort of stuff (which isn't silicone, apparently). I doubt there is one single one shot solution, but moniotring humidity levels is a vital first step, and I'd recommend you get a couple of such devices. I use Omega dataloggers, which cost £50 a shot, to monitor temp and humidity in buildings, which then plug into a USB port and give you a nice graph af temp, humidiy and dew point over a period of up to a month or two.
Yes, you need to make sure that all outside paving is well below damp course level, confirm that you actually have a damp course!, check every last possible source of pipe leakage, including such tricks as puttting drain testing dye into any waste pipework and seeing if it shows anywhere, keeping the place as well ventilated as you can, reducing generation of moisture as much as you can, wiping up any condensation on a daily (at least) basis.
Its a tough old job, but rising damp is actually quite rare, as Canardly says. I've been doing building defect diagnosis for around 40 years, and its rarely all that straightforward, and does involve a bit of science.
