It's true people are being stopped from taking photos, but I've never read from a photographer that he's been arrested. Stopped from taking photos, yes, but on no photography forum have I seen someone being arrested, so, like Dave, I'm inclined to just call usual Daily Mail bullshit.
Some of the public, and PCSO it seems, are concerned by those with DSLRs, and there is a case for those who use tripods in a built-up public area (they are quite a safety hazard), but it's rare. Random Joe Tourist with his point and shoot will have no bother whatsoever.
For the record, this summer I was down in London with 2 DSLRs dangling around my neck and a big rucksack (which could have contained a BOMB!) in and on some of the the most popular tourist destinations, and no one even bothered glancing at me.