Its a Freepost number, so just write it on an ordinary envelope, for goodness sake!
Why am I even bothering to waste my time typing this? There are far bigger issues at stake, like "Do we have confidence in the Rakon expansion plans?" I do, (I think...........?) and have sent off my cheque - although I admit I have been a little bit tempted to sell the existing shares to cover the $15,000 - and to take advantage of the present discount in case it evaporates.