Whilst typing there are times when instead of putting Cap Locks on, you simply press the key that looks like the up button and hold it down (soory do not know what this key is called) It is the same one if using brackets etc.
Any way, it is fine apart from when I type a capital M.
It seems to hold and repeat the capital m, thus looking like this MMMMMMMMMMMMMMMM.
Any ideas why or how I can stop it? It does not happen on ANY other key, and there is nothing wrong with the keyboard.
The key to which you are referring is called the "Shift" key (there are two of them on either side of the keyboard).
They are held down momentarily to make a capital letter. The caps lock keys will produce all letters in capitals.
Sorry, I think there IS something wrong with your keyboard because I cannot reproduce what you are describing. Try plugging in another keyboard to see if the problem continues.