Andrey,

Thanks for the pointer – I turned on PHP logging and found the problem-

PHP Fatal error:  Smarty error: unable to write to $compile_dir '/tmp/serweb'. Be sure $compile_dir is writable by the web server user. in /home/serweb/smarty/Smarty.class.php on line 1102

Down to permissions on the /tmp/serweb directory – all now working, thanks!!