To enable this, create a smart collection named All Products and set the condition to 'Product price is greater than 0'. You can create a collection through the 'Collections' menu in Shopify admin. Or you can turn this section off through theme settings.
How could I forget? We've reduced our UK postage rates to an amazing £3.00 for your whole order regardless of size or weight. If you spend £100 or more delivery is free. That's the whole of the UK, not just the mainland.