@Petecorbs I wouldn't look at chains and sprockets yet, just changed mine, and unless it is a daily driver, it is a long process, RAVE is good at showing you what to do and can be done with head in-situ you need a timing set with locking pins etc. I took head off mine as it was cracked. If you need any help let me know got plenty of help from all on here but I have been through the whole process as a novice.
The sprockets were badly worn on mine and chain stretch was excessive after 180k miles you would expect that. I ended up buying a complete timing replacement kit from Advanced Motor Factors was cheaper than buying chains and sprockets individually.
Let me know if you want to do this I can guide you where I bought the parts.
I will try and find the threads I made, I think everyone on here knew my issues
but were a great help.