1. Browse a paper catalogue with thousands of items (audio equipment, kitchen accessories, jewellery, toys, ...).
2. Write down the 7-digit code for each item you want to buy, on a slip of paper.
3. Go to the nearest Argos store (there are many).
4. Queue (line up).
5. Hand the paper to the cashier and pay for the items.
6. Wait ~5 mins until your order number is called, then collect your items.
(Everything is in a warehouse behind/below the store.)
This how it worked almost 40 years ago when I first shopped there. Today, it's very similar, except that:
- you can reserve online, so you don't have to worry about an item being out of stock
- you can pay extra and have the items delivered
- they have a much thicker catalogue, with many items that are delivery-only (similar to any other online retailer)