How to lock Ford Focus engine for removing timing assemble

Hi there. My little Focus suddenly stopped working a few weeks ago. The break down mechanic said that the timing belt had gone. After getting the car home I examined the timing belt myself and it was fine. A little worn but still holding strong and so were the tensioners.
The problems was when I tried removed the spark-plugs. The plug that was in cylinder 1 had a bent head. Looking through the hole I could see an impact mark on the piston head and a small disc like object next to it, (a valve head). The timing belt has not gone so how could this have happened. The other cylinders seem fine as well. Also, is she repairable?
Its a Petrol 1.8 16v Zetec
Thank you for any advice you can offer
Anna

Hi there.
I have been unable to remove the lower timing belt cover due to a rounded bolt so I cant see whether its all in good condition. I can turn the engine but as soon as it hits about 11 o'clock it stops dead. If I turn it counter clockwise it gets to the same point and does the same. Through the sparkplug hole I can see what must be one of the valve heads laying on top of the piston. It looks as if it broke off and the piston rammed it into the sparkplug, crushing its gap and denting the piston head.
When it happened there was no indication that anything was wrong. No bang, shudder or anything. It just wouldn't turn over. The engine is a high miler but it has always felt as tight as a drum. Hopefully its just cylinder 1 that is damaged. I will remove the head to see what condition the cam shafts are and then the piston cylinders later this week. Would it be possible to just replaces the valves and repair or replace the piston head?
Thank you
Anna

Belt is missing teeth and wont turn everything to top dead center together. Why can't the cams be turned into position without the belt on?

Thank you, total novice in this department. I thought it could be something like that. Would it be the best to put the new belt on loose. Turn the cams by the crank, then loosen the cam sprockets. Then turn the crank to top dead center?

Thanks, that is what I decided to do before I read you reply. I am glad I made the right choice. Unfortunately I do not have an impact, and cannot break the cam bolts loose. I had a friend hold a wrench on the cam flats. Any suggestions?