I have a 2015 1.0 ecoboost zetec S and I’m thinking about getting it lowered 45mm has anybody had it done and had any problems being lowered by that amount? Cheers 

You will be ok at the rear its the front where you will have issues with camber and wearing the inside of your tyres out very quickly unless you get decent coil overs with adjustable top mounts so your camber can be set up correctly.

I see a lot of cars lowered where this isnt addressed and it can be very dangerous as the tyre isnt in full contact with the road surface so your breaking distance goes up and traction is compromised.

here is a pic of front shocks with the adjustable top mount

https://uk.carthrottle.com/products/bc-racing-br-coilovers-for-ford-fiesta-mk7

Too add you can adjust the camber a bit on the OE shocks / and after market where the bolt to the hub but when you are going as low as you stated you dont have enough adjustment although I have seen people use thinner bolts to help with this but this is not a safe way to do it.

Okay thanks for the information what do you think would be the best lowering it by with just springs? So I don’t get any problems thanks 

Ford used to sell Eibach springs that lower the Zetec S by 20mm (30mm for a standard model).  These were also recommended by M-Sport for their Modified STs. Lowering much further than that requires new dampers to ensure the valving matches the reduced piston travel.