Unfortunately how long is a piece of string.
Some trusts can be on the ball and others fail spectacularly at communicating results back to patients.
All you can do is keep an eye on how long it's been and then get onto them if the results dont show up. Often the have them but won't share them until other or all tests are completed. Really frustrating when you just need to know.
But remember, your only a statistic to them, not a feeling, breathing person.