Glen - at the very least demand a copy of the postal receipt,if he doesnt show it then he didnt post it full stop,then you tell him you want the full refund,i'm guessing it wasnt cheap?
If you have kept all dialogue with the guy then surely you can use that against him,threaten him with police etc...
Its the principal here,doesnt matter if its £5 or £5000,the guy is making money from you and maybe others through postage alone.
Sounds to me like robbie may be going through something very similar,maybe you should pm him and find out if you can work together on this.
Cheers stef