People had to pay for rations during the war (and for a few years afterwards, until 1950). Rationing limited the food you could buy, but it didn't mean you were gifted the food. It meant that certain items, especially things like meat and dairy, were only available in short supply and you were given a quota per week.

As /u/FlewPlaysGames says, rationing was a system to limit what any one person could buy, it did not mean that people received free or discounted food. Those that could afford it had been buying foods (and other items that were in short supply) on the black market during the war, provided you knew the right people it wasn't too difficult to obtain extra food - even if it was expensive.

The last thing to come off of rationing was meat, this didn't happen until mid 1954.

One unintended effect of rationing was that the general health of the population improved as they were eating more of 'the right thing'. There was a big push from Government for people to grow their own vegetables and even keep livestock in their gardens. Many of course continued to do this long after the war.

Recommended reading: Wartime: Britain 1939-1945 by Juliet Gardiner - the book covers many aspects of living in wartime Britain and covers food/rationing well.