The UK did relatively poorly economically in the first 35 years after WWII compared to the other main European economies. Some of this poor performance may have been due to adjustments to the loss of the empire (which largely happened in this period) (Some may have been due to Britain's economic policies. Some may have been due to other reasons.)

In any event, from circa 1980 onwards, Britain has been doing better economically than the other major European countries. Some of that was probably due to North Sea Oil. (Some might have been due to other things, such as Thatcher's de-nationalisation of industry and other economic policies.)

So, if the loss of Empire had a depressing effect on the British economy, it did not last very long. This could be because the Empire was not particularly helpful to the British economy. It might even have been a net drain rather than a benefit.

From 1980 to 2008 Britain was the only major European economy to grow faster than the USA.

Here is a look at GDP per capita compared to the USA (USA = 1.000) from 1980 to 2008.

UK:______1980 - .688, 1994 - .705, 2008 - .765

Germany: 1980 - .803, 1994 - .812, 2008 - .763

France:__1980 - .780, 1994 - .730, 2008 - .713

Italy:____1980 - .756, 1994 - .754, 2008 - .675

(Source: www.themoneyillusion.com/?p=5164)

So, British GDP per capita has been improving relative to the US between 1980 and 2008. Meanwhile, the other main European Economies were slipping relative to the US.

The UK economy has been doing better than the rest of Europe from 1980 to 2008. It was doing worse than the rest of Europe before 1980: Here is GDP growth for Britain vs other European countries for the decades after WWII:

UK:______1950-60 - 2.7, 1960-73 - 2.3, 1973-79 - 1.6

US:______1950-60 - 3.3, 1960-73 - 4.2, 1973-79 - 2.7

Germany: 1950-60 - 8.0, 1960-73 - 4.4, 1973-79 - 2.4

France:___1950-60 - 4.6, 1960-73 - 5.6, 1973-79 - 3.1

Italy:_____1950-60 - 5.5, 1960-73 - 5.3, 1973-79 - 2.6

(Source: http://www.rozenbergps.com/books/britain/kern.pdf)

By 2008, remarkably, Britain had become the leading major European economy in terms of GDP per capita. Ahead of Germany. (In 1980, Britain was in last place among the big 4 European economies in GDP per capita.) (Don't know what has happened since the 'great recession').

If some of this turnaround in the growth of the UK economy was due the adjustment to the loss of Empire not taking very long, this may indicate that the Empire was not particularly valuable economically in the first place.

The British government performed only one comprehensive cost-benefit analysis of its Empire and that was in 1957 in the aftermath of Suez. Harold Macmillan, the Prime Minister, concluded from it that decolonisation would not harm the British economy, which was moving away from trade with the colonies to Europe and elsewhere in the world.

While Britain's manufacturing economy boomed during the Victorian and Edwardian eras, it could afford to hold territories that were in no way advanced economically (e.g. large tracts of tropical Africa). The audit came in the post-war world where the British economy was declining relative to other major economies and public spending economies were deemed necessary.

You're right that Britain in some ways has not got over its Empire. British politicians still feel the need to get involved in conflicts and disputes that do not directly concern her. There is no correlation between the real mediocrity of Britain's situation and the outlook of politicians. The reason? Britain felt itself a victor in WWII and unlike France never suffered invasion and occupation. Britain emerged from 1945 with the psychology of a victor but with the economy of a defeated state. The prestige of victory overrode acknowledgement of Britain's real situation.

Source: T. Hopkins, 'Macmillan's audit of empire, 1957', in P. Clarke and C. Trebilcock (eds.), Understanding Decline: Perceptions and Realities of British Economic Performance (Cambridge University Press, 1997).