Geting correct jar to load in own server?

[sinver]

Hi all, firstly apologies if this should be in the server forum, but as it is an advice request I figured here was appropriate.

I have got myself a small space on "MClayer" using the multicraft file server to run a small server, mainly for me and the missus.

However, I followed the instructions for uploading the tekkit server zip, and renamed it as instructed. (I followed this: https://clientarea.minecraftlayer.com/knowledgebase.php?action=displayarticle&id=46)

However, despite selecting "craftbukkit" in the jar selection part of my server controls, when starting a game, none of the tekkit items exist. For example, to test it I tried to spawn a copper bar, and it says that item does not exist. Any ideas what I am doing wrong?