This is amazing place to be leaving at and one should visit Barry at least once in lifetime if you are living in UK, however not only this place is amazingly lactated and with many great community it has some serious issue with clod walls and obvious moisture. There is much research and common sense knowledge showing that moisture is causing mould on the walls and in the air, it is not that we don’t have mould spore in regular house and it is only occurring at those seaside places. Mould is very effective leaving thing that will utilize every possible space it can and as much food as it can consume and convert in to energy will be utilized.
For those spore to develop in to mould many conditions has to be actually in place, first of all there needs to be enough humidity in the house and not enough air circulation to make the spore circulate in the air rather then stay on the surface and start eating organic matter. That is why it is strongly recommended to have air dehumidifiers in the rooms that one is experiencing some mould development, besides that you can always clean your walls with dettol or other disinfecting substances that will help to fight spores that are very origin on mould structure in the house.
Unfortunately Barry and Cardiff is presented with lots of moisture in the air, not because of all the rain that we have in Wales.
Using passive dehumidifiers and cleaning your walls with domestics or other strongly antibacterial solution will help to fight spores that are main cause of mould development on the walls, when it comes to carpets one should be careful with use of any strong antibacterial chemicals as those can damage carpet irreversibly. Best of luck with your fight.