It's no Mad Men, but this tale of 60s student flatmates is shaping up nicelyIthink there's going to have to be a moratorium on shows set in the 1960s until we've all had a chance to let the memory of Mad Men fade. Let time sully its perfection just a little before you serve us up another.There was much to recommend White Heat (BBC2), the six-part series by award-winning writer Paula Milne, about a gang of 60s flatmat…