I was sent a link today to an online petition to reduce the classified period for census data from 100 years to 70 years. http://petitions.pm.gov.uk/CensusInfoFreed/
This is actually on the E-Petitions section of the 10 Downing Street website. Petitions can be signed by British citizens or residents
I have signed the petition, which now has over 1500 signatures. I am not sure if it will have any impact, but it has to be worth trying. Another 3 censuses worth of information now would be well worth having.