I think this sums up your rights as a photographer in the UK.
http://www.digitalcameraworld.com/20...ltimate-guide/
So be clear on your rights and what is breaking the law. So many people will miss quote the law or apply restrictions which do not apply to a public place.
The number of cases of police harassment appears have died down compared to a couple of years ago, probably because of the number of lawsuit settlements each running into several thousand pounds against them.
Shopping malls, National Trust, Railway Stations and The underground to name a few are the areas to watch out for. They may have limits on photography as a condition of entry. Legally they do not have much that will stand up in court regarding the photos for personal use but they have the right to evict you and worst case give a lifetime ban.