Last time I used click and send which was of course back in April you purchased extra cover using the red reg post lodgement forms, there was a box to tick for buying c&s extra cover. I don't know if the same form is still in use as reg post is only available for letters or if there is a different form and I cannot ask at my local PO as it would be rather a long drive, walk, and swim, lol. I am sure somebody else will have a PO which is as clued up as mine, if not you will just have to wait until the end of Oct when it will be able to get to the PO in 5 mins