Try this, and make sure that there is no space between -u or -p. And if you are using PORT
you need to write it differently. The password parameter must then be --password=
mysql -hmydbserver.co.uk -P 3306 -uUsername --password=yourpassword
Since 3306
is the standard one you could leave it out, then you can write it like this.
mysql -hmydbserver.co.uk -uUsername -pYourpassword
If you want to pass with a command, do it like this.
mysql -hmydbserver.co.uk -P 3306 -uUsername --password=yourpassword nameofdatabase
-e "SELECT * FROM tablename"