Hi AJL
- Unannounced, however the first initial audit is announced.
- Tesco auditors are very strict. 
- I wouldn't say they are expensive but they have a lot of guidance's (Tesco Requirements for suppliers) , and you will need to create a gap analysis between your current situation and Tesco standard (is a time consuming task)
- you will find differences, for example Tesco has their own special procedures (Tesco Requirements for suppliers) for Withdrawal / Recall, you will need to remember about this to include in your procedure next to Morrisons and JS standards. Slightly different microbiological standards or whistleblowing