why have my exterior walls got damp patches since i got cavity wall insulation

Extra air bricks will not help as the cavity is now filled - the cavity need ventilation only when it is a cavity ! It is often the case when retro fitting insulation to a cavity wall that it causes unforeseen problems. The problem you are encountering sounds like damp bridging around cavity wall ties - the external walls are not waterproof and over time the water builds up - it is theoretically meant to run down the inside of the cavity and harmlessly away - keeping the cavity ventilated helps the moisture collecting on the inside safely dissipate. Retro fitting cavity insulation causes the water to build up on wall ties and leak out. I'd suggest coating the walls with "Ronseal" or similar product to make the wall less porous and may

Your cavity wall insulation is guaranteed for 25 years, paid for by the company who installed the insulation. If you contact CIGA 01525 853300 (the company who produces the guarantee) they will be able to help you. Kind Regards Helen Gabriel Insulation