If you're self-catering your best bet for supplies is the local supermarket: the warehouse-style Pak 'n Save is cheap and found in most large towns and usually stays open until at least 8pm every day. The less common Big Fresh is also good with many products available loose in bins so you can pick as much as you need. Failing that, you'll notice a marked drop in scope and an appreciable hike in prices at the neighbourhood superette - IGA and Four Square are the biggies. Convenient corner shops (or dairies), stock the essentials, but along with shops at campsites, also tend to have inflated prices, more so if located in isolated areas or anywhere with a captive market.