As you are probably aware under current & proposed 'Health & SafetyLegislation' it is you the owner/occupier who is responsiblefor ensuring that any work undertaken at your premises conform to all Health & Safety Policies. With regards to external window cleaning this means that you will either have to have ladder ties fixed to buildings above 2 stories (this work must be carried out by a registered installer and you must receive a certificate of compliance), ormake it possible to have the windows cleaned externally from the inside, even doing this means that you will have to supply a fixing for a harness (again this work must be carried out by a registered installer and you must receive a certificate of compliance). You will also be responsible for having these fixings checked & recorded by an approved examiner on an annual basis.