Well believe it or not i (sceptically) ran an engine flush through on the weekend and re-checked the compression it now reads -

1 - 180
2 - 175
3 - 181
4 - 173

Weird but if its worked im happy!

The only issue i still have is that there is a very loud clattering noise when im at between 1500 - 2000 rpm on light throttle, its driving me insane and i dont know what to do, i would really appreiate the help

Thank you for your replys so far