Use public UK benchmarks (e.g., Platinum Prospects niche benchmarks), triangulate with 2-3 agency sources, then adjust for your niche, creative maturity and offline tracking.
Steps
1. Pull your niche + platform from a UK benchmark source 2. Note the range (low-high) and your position 3. Adjust: subtract 10-25% if your offline conversions are feeding back for 90+ days 4. Adjust: add 20-40% if your creative is under 6 months old or niche is highly regulated
Use it to set targets
Aim top-quartile, not mean; mean hides under-performers.