Thinking about changing the timing belt on my wife's Citroen C4. Do I need to purchase the special tools specified in the Haynes manual, if not can something else be adapted to lock the cam shafts/crankshaft in place?

At least tell us the engine. If it's the 1.6 diesel unit, I will be able to offer advice.

Sorry, no its a 1.6 petrol in a C4 VTR

By looks of whats shown online they look fairly specific.

If it's the 16v engine you should be able to use drill bits forfeit the cams flywheel locking tool you may need the correct tool or maybe a drill bit !!!

Can you get at the belt to cut the old one in half round its circumference then slip the new one along side it? Then cut the old one off altogether and slide the new one home.

I would recommend a timing belt kit and water pump if the car has done a lot of miles , can't remember offhand what the service interval is but is it worth taking a chance?
If the C4 uses the normal Citroen timing tools they aren't a lot of money , the biggest problem if it has just a single crankshaft pulley bolt is getting it undone, a decent air wrench helps although I have had one shear off which took a while to drill out .

I would recommend a timing belt kit and water pump if the car has done a lot of miles , can't remember offhand what the service interval is but is it worth taking a chance?
If the C4 uses the normal Citroen timing tools they aren't a lot of money , the biggest problem if it has just a single crankshaft pulley bolt is getting it undone, a decent air wrench helps although I have had one shear off which took a while to drill out .

Hi if you pop into the garage you can borrow my set (ebden's)