Years ago, we lived in Southwark, in an attic flat in Trinity Church Square, painted bright blue, with paint from a shop just north of the Elephant and Castle.   The surrounding area was deeply dingy, little known streets, cheap housing, sandwiched under the railway tracks between London Bridge and Waterloo.   Today I crossed Blackfriars Bridge at lunchtime, visited Purdy Hicks in Hopton Street, saw the exhibition by Julian Stair at Contemporary Applied Arts (pots for £36,000) and had lunch at The Table in Southwark Street, designed, I presume, by Allies and Morrison.