Citroen C3 squeal

[mgroadster]

After a few miles a high pitched squeal starts from the n/s/f on my wifes C3. I believe it is something to do with the caliper. I took the wheel off and then placed my foot on the brake. It took a while for the caliper to release. Could that be causing the squeal? I fancy that as my theory.
If I jerk the steering wheel to the left I can get the squeal to stop temporarily.
You thoughts appreciated. cheers.(doesn't do it when driving from cold)