Have used Nationwide Pathology for both fit-to-fly and Day 2 testing on several occasions having searched through many other options. Prices are very reasonable, test kits are dispatched same-day, and they include pre-paid Tracked 24 envelopes. Results have always come back by email and SMS within 2 days. They went above-and-beyond recently when Royal Mail delivered my test sample to them 20hrs late - NWP still got the results to me that same day in spite of it being New Year's eve. Would definitely use them again.