Collation I did check already. No differences.
Have not checked the Apache version or PHP but I did manage to resolve the issue.

I had backed up and restored the full DB (3 companies) using phpMyAdmin. After I did a fresh backup of the one relevant company in the old and a restore of that backup  in the new instance from within FA all was well.

I don't understand what difference that makes, but it worked.

I am in the process of moving an FA instance from one host to another.

Have copied the files as explained in other posts. Exported DB from old instance and imported into new instance (using PHPMyAdmin).

I can login to the new instance without trouble using the same credentials as the old one.

However the transactions shown in the new instance look different from the old one. Have trawled the underlying DB and can find no differences between old and new. Yet old one shows in customer transactions:

Sales Invoice    350    492    681    08/03/2016    09/03/2016    Village Greens    Village Greens    GBP    5.60   

And new one:
Sales Invoice    350    492    681    01/04/2016    11/04/2016    Food Float    Food Float    GBP    5.00   

Note that transaction#, order# and ref are all the same. Yet dates, customer and transaction itself differ.

I suspect it's a setting somewhere on the new host causing this, but no no clue what it might be.

Any help appreciated.

D Hoogmoed