Who will decide who will be the next king of britain? whether the throne will be passed to william instead...?

of charles or vice verce?

The only person who can make that decision is Prince Charles. He is the heir to the throne but is perfectly entitled to abdicate, I would be surprised if he was not entitled to refuse to take the throne in the first pace but I'm not sure. So it's up to him really... poor chap has been in training for so long tho - can't see him turning it down at the last minute can you?

He could convert to Catholicism of course - that would bugger it up a bit!

Charles will take the throne. The throne is taken over by the oldest child.

There is no such thing as a King of Britain. The next monarch of the UK will be Prince Charles - if he is still alive when his mum departs.

there may not be any such thing as a "king" of great britain but there is a Queen who represents not only great Britain but also the rest of the commonwelth Australia,Canada etc.. i dont know what the comment above saying t"here is no such thing" is about.. considering the Queen is coming to Northern Ireland soon..not just this fact but also, the union flag hangs outside her official residence and have you seen the royal flag? it contains a symbol for all the nations of great britain including ireland..also why if she doesnt represent great britain would the queens anthem be played at northern ireland matches.you really should research more, if you dont know enough and not just answer with what you "think" to be right.

There is no decision to be made. As the rules stand presently, the first male child born to the reigning Monarch is heir apparent...there is no skipping over from one generation to the next. Charles will be the next king unless he dies before his mother our present Queen Elizabeth ll

It will pass automatically to Charles, but if he dies before his mum / abdicates, then it will be passed to William. If William is unable to take the throne and he hasn't had any kids then Harry will be king.