You mentioned the campaign type is Performance Max - that explains most of the breakdown. PMax is a black-box traffic grabber, not a lead qualification engine. When a manager quotes "50 leads" without filtering for quality, they're measuring vanity events, not real customer journey nodes.
At £750/month, you're paying for basic campaign management, not proper funnel architecture. A decent setup would have lead quality thresholds, geofencing for serviceable areas, and a logic branch to segment out spam or out-of-territory enquiries before they even reach your CRM. That's not happening here.
What I'd do right now: demand a channel breakdown - Search, YouTube, Display - plus a raw search term report. Then pause PMax entirely and rebuild a Search-only campaign with tight negative keyword lists and location targeting. Anything outside your service radius gets a hard block.
Also push for a validation step in your lead capture: a phone verification or a simple address-prefill filter. That turns form fills into qualified leads at the trigger point. If they can't implement that, you're burning money on empty journey nodes.
Honestly, cut the agency loose. Find a freelancer who understands lead scoring and can map your customer journey from ad click to booked job - someone who treats each lead as a data point, not a report number.