2002 Fiesta - I have a thin flexible alloy strip, about 400mm long and 15mm wide, hanging from the bottom of the radiator. It's foam backed on one side and has what look like alloy cooling fins on the reverse. The foam has mostly gone and the fins have mostly corroded. Can anyone tell me what this is for and if it needs replacing please?

Sounds much to me like the air conditioning fins, its only to help disipate the heat of the / spread the cool around the aircon. If you have only lost one, dont worry about it, if they are all falling off then maybe you should worry.