Clubman, thank you. I know what a management company is. I consider it the most effective way to notify other residents of a potential electrical fault.
Thanks everyone for all the advice. Opened it up and had a look but couldn't see anything that looked dodgy. Couldn't see any thermal cut out. Hoovered it out so will wait and see what happens later tonight.
Thanks everyone for your advice. You have just saved me the cost of calling someone out to look at the heaters. Looks like giving it a good hoover did the job!!