Doh...Solved it. Here's the answer for anybody else.

On the RadioButtonFor, introduce a new id :

Code:
@Html.RadioButtonFor(model => model.CustomerLoanOfVehicleValue, "FCL", new { @class = "optVehicleExt", @id = "FCL"})
Make the @id unique for each radiobutton then in JQuery as normal you can do:

Code:
$("#FCL").click(function () {
            ............
        });
Works!