Just make sure you post back here when the other letters arrive saying that failure to pay will result in a charge of £xxx, it's all B*llocks, just be clear that it is not a parking ticket (only local councils can issue them), it is an invoice.
why were you in aldi for that amount of time? you could of cleaned out the whole store by then...... or did your shop take 5 mins and the rest of the time was spent in the queue??