Thanks guys - Easy Tune sets thermal alarms at 40C as a default, so was concerned about the temp because my alarm was going off. I've never seen the PCH chipset temp above 52C though.
By the way, this is first build where I've used Arctic Silver thermal compound (I'd been using the stock compound on Intel's heat sink/fan). Seems to make a noticeable difference.
I was surprised to see, when I took the old mobo out and removed the heat sink/CU chip, how flaky and dry the Intel-supplied heat sink compound was. It couldn't have been doing much anymore.