Excellent it's good to find someone with the same board and an (almost) identical chip! Thanks for the tip, I saw those a while ago but thought being passive it'd be worse than the one i've got with the fan on top. Might be worth considering.
I think at the end of the day I spanged £16 on a heatsink that didn't really fit, I had to bodge it with the fittings from the original and didn't seat right. And everything I watch can be transcoded on the multipliers i'm playing with, even when locked onto 6x, I might just leave it as is. Does seem a bit like buying a 911 Turbo and slapping a 25mph limiter on it, but i'm bored of pulling my hair out!