"either waiting on the user for something (more info required and they're not answering phone/e-mails), or waiting on a third party (ie, order to arrive, PC supplier to come and fix the PC"
Yeah - waiting for the user is a definite clock stopper , but the all the other examples come down to what was agreed in the contract i guess - even if its a internal contract between departments.
If the users say they will provide their own spares for example, then its a clock stopper when thats needed , but if they only really pay for the bare minimum in SLAs/ parts supply / support hours etc etc it ends up with you not being able to provide a credible support service , which makes us look bad and is incredibly frustrating for the end users - who think its our fault.
Example A - I worked at a company that provided wifi for other small companies who never paid for enough coverage for their sites - just enough to tell their customers ( the public) they had wifi.
This resulted in a helpline who could do little more than sympathise the user, or say things like "Have wonder around waving your ipad in the air and look for a mast thingy"