I don't think you're being altogether fair to SLEC.
The delivery time may be longer than for most of the UK, but that's a consequence of where you live and there ain't much that either Royal Mail or SLEC can do about that.
The reason for the high cost is the quantity of additional packing required to prevent the Royal Mail Second XI reducing your precious sheets of balsa to splinters. The postage price goes up in blocks, so a 2.1Kg package costs exactly the same as a 4Kg one sent the same way (check it out).
Quite apart from the weight, the size of the package @ 36" long obviates any other options. If you want a real shock then try getting a shipping price from DHL or UPS!! For example, I was quoted £83 to send ONE 550 motor to Trinidad; Royal Mail did it for a tenner.
Finally, please consider that SLEC will have to pay over to HMRC £1.34 of the £9.00 as VAT, so if the cost to them is £8.22 then they're actually losing out by only charging you £9.00.
Suit yourself, but I don't think you're going to do much better.
FLJ