I am always astonished when I see basses worth one or two grand shipped for peanuts. With the going courier insurance rate at £20 per thousand, how can such low rates be available? Do you know that 99% of couriers have very low liability limits when carrying musical instruments, if any at all? Take Parcelforce, for instance (aka ParcelFARCE): they're happy to take your insurance money, but in case of claim it's printed in their T&Cs that the max cove for musical instruments is £250!!! (Or, at least, that was what I saw last time I checked).
For basses up to a grand, i use UPS through Interparcel, and over that, UPS directly from them. Not cheap, but at least they insure the full amount.