I just about remember this as a child, In was at 11-12 too young to really get it, though the limited understanding I had, was enough to stay in the memory as sinister.
It was a product of the time in that it took what some saw as the post war advance of 'big government' to one possible conclusion. Just like the best sci-fi, of the best, understated British kind, with the pessimistic view of a future inherent in this genre.
But I cannot agree with the idea that this series foretold today, the recent, under the previous government (though some may cite the handling of the 1984/5 miners strike by the government of the day as well) questioning of civil liberties, the expansion of a 'police state', all the CCTV, the DNA database, the (latterly) unsuccessful attempts to lengthen detention of terrorist suspects, were not, unlike in '1990', the systematic work of a very authoritarian regime. Rather it was driven by fear. Fear of hostile media on crime, fear of, if a massive '9/11' style attack happened, being thought of any neglect that allowed an attack. An obsession to meet targets to produce evidence of 'fighting crime'.
Reality check - most CCTV systems in the UK are not controlled by the police, the state in general, rather they are operated on private premises, shops, shopping centres, business parks etc. Central control only exists in the third Bourne movie.
For all that, it does now seem that the coalition are going to roll back many of the controversial changes of the last 15 years or so. Because in a democracy, a change of government can do this. Unlike the world depicted in '1990'.
Still, I would love to see a DVD release, it was a superior series which did make for useful comment of a possible future, some of which did occur, though not so far in the all encompassing way of '1990'.