Well if I lived in South Wales i'd say it was crap and don't bother starting
There are a lot of threads on here about starting up do a search. If your job is well paid (but stressful) why do you want to start carpet cleaning? What backround do you have and could you apply that to starting your own business? In some respects carpet cleaning can be seen as money for old rope because it can be deemed as being easy, and it is to an extent, but you will need some training to avoid the risk areas, descent equipment and a good marketing budget. The job is relatively easy, getting customers, recommendations and a descent living is not. Be prepared to back yourself financially for 2 years to account for the lean times and if needed be prepared to take on a paid part time job. Some start whilst still keeping the day job as a safety net and cleaning evenings and weekends as a trial to gauge the market and it's potential. Your first step may be market research, basically knocking on doors and asking the question about professional carpet cleaning, are they interested and what would they be prepared to pay. Do a sample of several different streets and demographics. Now may not be the best time to make the leap, and the market research will help with making your mind up.