I have a ford focus 1.5 petrol ecoboost. I very recently had a new clutch,  concentric  slave cylinder and dmf supplied and fitted at a cost of  nearly £1300 . Now when I’m changing gear more in 1st and 2nd there is a whining noise plus a  noise when changing gear is quite loud, before having the new clutch etc fitted there was no noise when changing gear and the gear changes were a lot quieter and smoother than there are now. So I took it back to a1 clutches in Tipton where it was supposed to of being repaired they  are saying there is nothing wrong with it and that the noises are a characteristic of the ford focus. I feel like they have took my money and now don’t want anything to do with it. But I think I’m need to get a second opinion before I get trading standards and the motor ombudsman involved as I am not going to let this sham company get away with ripping off and thinking this problem is just going to go away 

they seem well rated

https://www.trustpilot.com/review/www.a1-clutches.co.uk/location/tipton

based on that, I would suggest

1) you got back someone else's gearbox

2) they forgot the oil

3) it was always like that and you are mistaken

the gearbox is pretty much not touched to change the clutch, only removed and refitted... so likely to be the same as it was beforehand - the clutch failure mode is of interest, as if it wasn't operating correctly and the car used for a long time it may cause box wear...

what mileage, how many owners, main user driver skills ?

if low miles and needs a clutch might have been abused, if high miles might be worn out

re the points above

1) unlikely

2) possible - get it checked by third party

3) likely