Thanks for the replies guys,

Lee, did your car have a very slight miss when it started ticking? Mine did but it was nowhere near as bad as if i pulled a plug lead off for example. Thats why i'm pretty sure it's one of the valves not opening properly. I'm hoping it's nothing else as all the normal signs of big damage are not apparent i.e smoke out the back or froth in the header tank e.t.c

Cheers,

Dave