Please feel free to delete this but it's good information from years of trading:
There must be quite a few sales lost on here because people are unwilling or unable to ship.
First I'll address packing a bass, if you don't have a suitable box then go to your local bike shop and ask them for a bike transport box. These things are used to ship expensive bikes from the Far East and are really tough as people who've bought from me will testify.
They need cutting down to about half of their height and yes it's a bit of a mess on but if it gets you a sale? You'll also need brown packing tape, a sharp stanley type knife and newspaper to scrunch up around the bass. This is very effective. If your bass is in a hardcase then you can even just cut some smaller boxes up and wrap the case up in them.
Couriers:
When a seller says "you can arrange your own courier" they don't seem to realise that you have to pay twice to do it that way. Once for the trip to collect it and once for the delivery so twice the cost to the buyer. This is just being lazy imo, all you need to do is fill a form in on Interparcel's site, pay with a card and prices with UPS start at £6.99 + vat!! Very cheap.
What I'm saying to sellers is, put yourself out a bit and show willing, yes it's a bit of a hassle but if you get a sale so what?
feel free to shoot me down in flames. Or pin this.
Have a great day! Tom