Hello my timing chain snapped on my Ford s max 1.8 tdci 08 plate.
What would your advise be repair my engine or replace the engine thank you in advance 

I believe the 1.8 litre is a belt not a chain but when either of them snap something coming down meets something going up and damage results. 

Without knowing the degree of damage it's difficult to suggest the correct course what to do. If you can get a garage ( non Ford you know and trust would probably be better) who could give you an estimate for repair  that may be your best option. If your present engine was performing well and you've had it a while it may be better sticking with an engine you know a little about rather than buying an unknown engine with it's problems. There are units coming up on e bay all the time from scrapped cars if you decide to change, but beware if you buy one I would change the belt before putting it in, you can't trust what people say has been done to the engine.

Todays top tip, changing timing belts is better done 6 months early and with 5,000 miles in hand on the recommended limits rather than 1 day late and a mile too far.