We do, and an agency’s risk works differently from a sole trader’s. If you send someone to clean on your behalf, you can be held liable for what they do, even when you were nowhere near the building. Lawyers call it vicarious liability, and it applies to employed cleaners and, depending on the arrangement, to self-employed cleaners working under your name.
So a subcontractor’s own policy does not automatically protect you. Tell us how your team is made up when you quote, including casual and seasonal help, so the cover matches the way the cleaning services are really organised.