Basically there was not enough airflow around the PC, it was right up against a wall and there was no room for airflow around the PC and behind it. Just pulling the PC out from the wall by about 10 cm reduced the temperature by 5C and taking both side panels off brought the temp down from 70 C to 50C, quite an improvement!
This is such an obvious thing to do, but I just didn't think of it
Anyway, at the expense of making the PC sound like a hoover, I have fitted two chassis fans. Now with both panels in place and with the PC placed back where it was the temp is 55C while it is idleing and hovers around 60-62C when it is maxed out, the mobo temp is now always at 25C.
Sorted... well almost, now i just need to replace all the fans with quiet ones.