I have no direct info or experience, but my own opinion, for what it is worth, would be to ensure the pallet is wider than the axle, by a good few inches. I'd also be looking at some kind of wooden protection for the ends of the axle. As for courier company recomendations, just search on line for reviews, or possibly a classic car forum (check post dates first to make sure it is active and current) as they are probebly more likely to have experience of sending something like an axle.

Regarding the axle weight, unsurprisingly i could find nothing specifically relating to the pilot, but i did come upon a post from a US based British car forum, and a discussion on Triumph TR7 V8 rear axle (stock and upgrades) weights. There were 4 mentioned and ranged in weight from 149lb to 195lb, which is from 67.5kg (ford 8") up to 88.5kg (dana 44). I think it would be very unlikely for the pilot rear axle weighed more than that.

I had to get a 12 foot long exhaust delivered a couple of weeks ago, all in one piece. I used the website AnyVan, but then rang them up with specific dimensions and they found someone for me.