We have water coming in on brick work round sides of a new window.

The people responsible for fitting the window obviously haven't sealed the opening sufficiently. If you have rain water running down the wall over the window then a "head drip" should be fitting to throw the water away from the window.

The thing with older properties is they didn’t have much ingress protection around window and door openings, so my advice would be to fit a drip to the external head of the window/door to make any rainfall fall away from the opening. In cases of repainting, take all paintwork back to original stonework where possible and seal it all before repainting. Sealer must be impregnated into stonework (ie: stabbing action) to make sure any water doesn’t seep through, and in some cases make sure there is a good seal around window (Silicone) after to make sure any water doesn’t get through.

A head drip bar wont stop the water penetrating through pourous brickwork the bricks will need sealing

there is a number of reasons this could be, to blame the window fitter would be unfair, the only way to solve the issue would be a site visit as this could be an issued with the cloaking, roof or the mortar joints