<input type="text" name="Property_FullPostCode"
            data-val="true" data-val-required="Invalid postcode" data-val-regex="Invalid postcode"
               data-val-regex-pattern="myregex" **data-val-regex-modifiers="i"** />

<input type="text" name="Property_FullPostCode"
            data-val="true" data-val-required="Invalid postcode" data-val-regex="Invalid postcode"
               data-val-regex-pattern="myregex" **data-val-regex-modifiers="i"** />

$jQval.addMethod("regex", function (value, element, params) {
        var match;
        if (this.optional(element)) {
            return true;
        }
        **var modifiers = $(element).data('val-regex-modifiers');**
        match = new RegExp(params**, modifiers**).exec(value);
        return (match && (match.index === 0) && (match[0].length === value.length));
    });