My NPC has an AI package that says offer services and continue if PC near. All the time tabs are set to Anytime, so he should sell always.

The tickboxes are ticked for which services to offer.

But when i speak to him he has no barter option to click on.

He has a chest underneath the Chestnut Handy Stables. Does it matter if my NPC is inside or outside of the stables in relation to the vendors chest?

Npc need to be default Merchant Class or Custom Class with offer services checked off. Check your class

Read this..Very closely..

http://cs.elderscrolls.com/constwiki/index.php/Adding_Sellable_Items_To_Merchant_NPC

Ok I've done everything it says and still nothing.

I've set the container ownership on the container and as the ref for the NPC.

The NPC is a Merchant Trader so he should be selling.

I can't think what else is to be done.

I've set up an NPC who sells before, but I used an existing merchant (Shady Sam) as the template and just changed the ownership and ref and all that. I'm sure I've done everything.

I have no idea what you're talking about but I will say this incase it helps. If your disposition is 0 a merchant will not trade you and you must bribe them to get that disposition back to be able to trade. (either this is true or I am getting myself confused with another game)

Thanks but that is not the case here. I have a high disposition with them.