Fiesta roof bars fitting query

Hi all, R reg Fiesta 1.25, 3 door. Need to get some roof bars for it, but having trouble finding the right ones (checking on-line at the mo-not been able to get out and see some 'in the flesh'). This Fiesta has a 'smooth' roof with a black plastic insert running full length. I assume that this unclips/removes somehow to allow bars to be fitted, yes? How do I remove these bits?? The bars I have looked at seem to be for cars which have the old fashioned 'ledges' which the bars clip onto. I dont have a handbook or manual, so at a bit of a loss which ones to get. Anyone help-maybe someone knows the specific bar model number I need?? cheers