Supporter services actually got back to me the day after my post above and a voucher duly appeared in the post which was successfully exchanged for a new shirt just before the Saints game. Satisfied customer here
Was looking to wear a new shirt ordered through the 'show your colours' thing but so far I have no idea how to get the shirt that I've forked out £30 for alongside the semi-final tickets. Tried redeeming the code with the email - fail. Tried contacting the club shop - fail. Tried supporter...