Right....... i think i have sorted it now... (famous last words i guess)
i stripped all the pc down, cleaned everything, and rebuilt it....
while rebuilding it i noticed my motherboard had an 8 pin & a 4 pin CPU connection, i had only got the 8-pin connection in (the manual says to use either 8pin or 8pin and 4pin, also i only used 1 x 8pin before the upgrade), i remember when putting in the new PSU that it only came with 2 x 8pin modules so i decided to only use the 8pin without the 4pin, i ordered a 4pin cable and connected that and the computer at the moment, feels nice and responsive...
after all this messaging about it i think it was just because i had no 4pin connector connected..... I feel rather stupid right now, but i do hope this is the reason and it stays working as it currently is