@phuzz - No. Currently the data collection is illegal. This means that spook agencies cannot (or at least have a harder time) use the data as a weapon against the populace because they are not supposed to have it. Whether it's for blackmail, to consolidate personal power, or just slapping down someone they dislike, it is much much harder to use data in this way if the source of the data has to remain covert.
If the data collection is legitimised, all bets are off. That will give a huge number of people the newfound ability to use the data and the court system to utterly fuck people's lives with impunity. We've already seen this with the RIPA Act. Now you think about all the data you're spaffing every day and tell me that you don't think that there's anything malicious that could be done with that.
The second point was that the spook agencies will ignore the rules anyway. They always have and there's no reason whatsoever to believe that anything is going to change.
The third point was that the Home Office is integrating all this data into one system. This is the exact opposite of what their job is supposed to be; and that is ensuring the security of the fucking people paying their bastard wages. Instead, they create a one-stop-shop of the detailed, intimate and personal details of a whole country for the browsing pleasure of anyone who can muster up a sufficiently competent team...and that would appear to include absolutely bloody everybody.