How often do you get your cam belt/timing belt changed on a fiesta ? 
ford website says 112.500k miles.

my car is currently at 90k and I’ve rung 2 garages. 
ford said it was around £800 and another garage said it was £600 ish. 
 

Who do I go with and why?

As you say it's 112,500 miles or 10 years on this engine.

Go with whichever one you trust to do the job correctly.  Pointless cheaping out on a cambelt change when it's only being done for peace of mind in the first place.  But also don't automatically assume a Ford dealership will be doing it correctly.  If possible, ask local friends or family members for trusted garage recommendations.  If that's not possible then you just have to use your best judgement based on instinct and online reviews.

Might get a better deal from a mobile mechanic. 

4 hours ago, TomsFocus said:

As you say it's 112,500 miles or 10 years on this engine.

Go with whichever one you trust to do the job correctly.  Pointless cheaping out on a cambelt change when it's only being done for peace of mind in the first place.  But also don't automatically assume a Ford dealership will be doing it correctly.  If possible, ask local friends or family members for trusted garage recommendations.  If that's not possible then you just have to use your best judgement based on instinct and online reviews.

The garage I normally go to is HereFORD specialist since they have been really good and honest with me in the past (they changed my actuator and give me my old broken one back). 
 

they are ones that quoted me £600 ish. 
 

Just found this. You have answered my post today about Cambelt change interval.

By George I've got it.     ta

 

come on Shrewsbury