Thanks for your reply
Am I correct to think that the total adjustment range a miner can make is to say (nonce + extranonce + timestamp), a total of (2^96)?
Changes to the timestamp or other parts of the candidate block gives the miner more nonce space to play around with.
Understood. However the question is, how big are the extranonce and the timestamp, are they both 32 bit as well as I've assumed?
Thanks again.