".....Should I use Ronseal Woodstain on it so it will do exactly what it
says on the tin? I'd hate to think of plain, untreated pine rotting away
down there....."

Unless your planning in advance then I wouldn't think you would have to
worry. Though you could make the box up in case , and use it as a planter
till it is needed


--
David Hill
Abacus nurseries
www.abacus-nurseries.co.uk