HSE Guidance is required to be looked at here I think re: DSE tests.
I doubt if the Agency is responsible, as the directives are workplace related, and since you are working in different offices with different equipment, that's just about an impossible task for any Agency to deal with.
Interesting question though.
You should ask the Agency directly as to their policy on the subject.
Sorry can't be of more help.
Pam
www.Aberdeen-Secretaries.co.uk 
DeskDemon Forum Board Staff