Welcome to the site mate.
Basically, you could check to see if the little brake pad guides are missing, and if they are there, put a little lube on them, and if not, replace them. The are located on either side of the brake pads, and sit in between the pads and the caliper housing.
They are a little piece of tin on a 90deg angle.
Also, the surface of either the disc or pad could be un even, this could also create the creek. The pads my have been machined beyond the limit and therefore the piston my not be pushing correctly.
You may want to go back and have a word to the people who did the brakes about it.
Someone else may be able to shed more light on the issue.
CAUTION: Slippery When BOOSTING!