How much would 2023 pounds in 1940 be worth today?

A British one pound note was worth $4.25 US currency exchange in 1940

The value to a coin / banknote collector today would depend on condition of note. You should be able to find on google search and Ebay

1 pound in 1940 is widely rated as very roughly equivalent to about 40 to 45 pounds now.

Please bear in mind that in 1940 income tax rose sharply (to finance the war) and that increasingly rigorous rationing came into effect. Some goods that are readily available now were scarce because they were requisitioned by the government: for example, photographic film was often difficult to obtain because over 80% of the entire output was used by the government, mainly for aerial reconnaissance. The production of most perfumes was stopped on the grounds that these were inessential luxuries and so on. The prices of essentials were fixed (and moderate). As a result, they was less and less to spend money on - and this in turn led to inflation. In 1940 prices rose by about 10%

I hope this answer is of use to you.

Joncey