In an ideal future British people would look to start businesses and create new income streams against a background of low taxes and without stupid bureaucratic interference from abroad. Only those who are unable to do this need be workers at all, but they'd get a much better deal in a free economy which is open to all and not just a few government supported foreign multinationals.
In such a future a realistic State pension would be available at the age of 55 because there'd be enough money in the economy to provide it.