Prioritize order accuracy, on-time dispatch rate, average pick-and-pack time, inventory accuracy, dock-to-stock cycle, and return processing time. Verify contractual SLAs for order cut-off, chargebacks, exception handling, and uptime for WMS/ERP integrations to ensure the partner meets your service and reporting requirements.

Key drivers include space rent, labor rates, throughput (picks per hour), storage density, packing materials, inbound handling and carrier access fees. Compare quotes using a unit-cost model (per-pick, per-pallet, storage per pallet UOM) and run scenario-based forecasts for peak and baseline volumes to reveal true total cost.

A central Islington location reduces last-mile transit times into city and suburban markets, improves parcel performance for same/next-day deliveries and offers straightforward road access to regional motorways and airports. For international lanes, carrier choice and hub connectivity determine lead times more than sheer proximity.

Require evidence of scalable labor pools, flexible slotting and temporary storage options, rapid onboarding and systems integration, plus documented peak staffing plans. Confirm the 3PL's ability to scale kitting, returns processing and value-added services while maintaining SLA adherence and transparent, frequent reporting.