You mean World War II?

A few of the references in the Wikipedia article Rationing in the United Kingdom: World War II are on-line. Specifically the article "British Food Control", from the Army News of Darwin (Australia), Thursday, 14 May 1942:

The British Minister for Food (Lord Woolton), has issued an order restricting the maximum cost of any meal served in hotels, or restaurants, to 5/- a head.

All meals are to be limited to three courses, and only one of these courses will contain not more than 25 per cent. of fish, meat or poultry.

The price of drinks to be served with meals will also come under the Minister's control.

In such restaurants where an orchestra is provided, an additional 3/- per head may be charged, and where a dance floor is available the maximum charge will be 10/-. All restaurants must be closed by midnight.

By this control of meal charges, it is hoped to make a more even distribution of "luxury" foods and cut off any temptations of extravagant spending in London, where previously, the normal charge at high- class restaurants averaged £2 per head for a meal.

Rationing among the general public was going on at the time.

The British Restaurant article has few on-line cites. There's a link to the Amazon page for

Atkins, Peter J. "Communal Feeding in War Time: British Restaurants, 1940–1947," in Ina Zweiniger-Bargielowska et al. eds., Food and War in Twentieth Century Europe (2011) pp 139–54 excerpt and text search

There's a "look inside" feature that may allow access to those pages, but apparently I'd have to log in, so I can't verify that it's of any use. (Unless you're well-off, I don't think you want to order the book!)

Well, I can't answer for the British, but America was rationing too, and here's a wealth of primary source documents: menus from NYC restaurants! [And you can help to continue to transcribe menus everyday for the NYPL!] http://menus.nypl.org/menus Just select decade: 1940s, and then go for 1943 for the height of rationing.