Well in reply to all the temperature stuff on the last page, once I got my system in the case the airflow over the SAS heatsink was still pretty minimal so I bit the bullet and slapped one of these on it:
http://www.zalman.com/global/product/Product_Read.php?Idx=133
Probably wouldn't recommend it unless you are ok with voiding your warrenty quite hard as it involves getting the SAS heatsink off (which is thermal epoxied on), cleaning up the chip and then mounting that heatsink (which mounts really nicely with the provided holes around the SAS chip, don't know why they didn't use pushpins when they have made the mounts...)
Results are much improved, the zalman gets warm but nothing like the extend of the old one (no surprise given its about 8x the mass) and the size of it means its much better situated to dissipate the heat.
Very pleased but yeah probably not wise to start butchering your £180 mobo if you like warranties and things and not having to scrape epoxy off the SAS controller die.
On another note I emailed supermicro US and NL support this morning to ask what the interface under the heatsink was and the NL guys got back to me within 7 minutes with an answer and the US guys within a few hours with the info, very impressed by the tech support email.