Hi Clive,
I tested by installing fresh copy of AEM6(without sp1) and introducing an error in jsp script. I see error for my file in error.log
Then I installed SP1 and created same error in jsp file, I am able to see the error in error.log.
I suggest you to restart your AEM6 after applying SP1 update. Then test again.
If that doesn't work, create a fressh install of AEM on separate port like 6502. Then apply SP update, restart your server and test it again.
Hopefully you should see errors in the log