Really for an expensive Air Rifle your looking to send through an RFD to be safe. Think the last time i sent RFD to RFD it was £25 and the guy had to pay £25 his end so it cost him £50 in total.
The last time i bought a Rife i drove to Reading for a really nice AA S400 nearly new paid £200 for it and was well worth the 80 mile round trip.