if a sliding door, that is padlocked on the outside for security and is the main entrance into  building is unlocked and the padlock is then locked shut onto secrung eye so that the door wiill not close fully can it be classed as being able to be opened without the use of a key?

If I have read it correctly are you saying the main entrance sliding door will not close properly because of the padlock that is secured to the security eye. Providing this will not prevent the door from being opened from the inside during the time the premises is occupied it would be acceptable and meet the criteria as being able to be opened without the use of a key. The only problem is the number of relevant person that may require to use this sliding door because the numbers are limited for a sliding door.