Wow. That sounds like a lot of drama for a company with only 6 people.
In such a small company there are a LOT of considerations with moving people around. Number one of which is cost. The network plug thing might not just be whether there is an actual plug in the wall but also if the router etc has space. Those cost real money to replace.
But there's more to it. I have a small office in which I (as CEO) was considering moving a couple employees around in order to facilitate communication. However one of the guys I was going to move smokes and the person I was going to put him with told me he'd quit if I moved a smoker in with him. I don't want to lose people right now so that plan was scuttled. The benefits of retaining both people outweighed (by far) the benefits of making it easier for a couple employees to talk about business.
It might very well be that the CEO initially thought they could move you but a personality conflict with another employee has stopped this and the CEO has no idea how to resolve it right now. It might simply be whether they have the money to make whatever changes they need to in order to make it happen. It might also be that someone is going to be fired (or quit) soon so they don't want to do anything until it's all shaken out and certainly don't want to alert anyone else.
However, there seems like there's yet another more serious issue here. You say
"It is causing a number of issues including being left out of decision
In a 6 person company, which has at least 1 level of management between you and the CEO, what decisions are you supposed to be included in? The CEO at this size retains very fine grained control over what gets done, by whom and when. If you aren't happy with how things like this work it's probably best if you move on. - side note: I used to be the CTO for a small tech company where both the Sales VP and I were left out of almost ALL the decisions - even though we were within about 20 feet of the CEO's office. So that part can happen regardless of where you physically are.
Regardless, it isn't your position to try and force the CEO to move you. It is your managers position to follow up. That said, it's quite possible the manager has followed up and simply hasn't given you the full details of what's going on. If I have someone going over their managers head on a topic that is between their manager and I then I'll move the non-manager right out the door. I did this last week with an employee who couldn't stay focused on their tasks and was constantly in my office because they didn't like their manager's direction. My time is extremely valuable and I put that manager in place so I didn't have to deal with those interruptions. Believe me that I know what that manager is doing and fully approve.
I suspect this is because my manager is seen as a threat (he is very
experienced, brings in a lot of business compared to our colleagues).
I also suspect some of our colleagues make their own sales record look
better by making out he is underperforming in some way (they are
missing their targets, but have been allowed to stay on regardless).
That entire paragraph is a huge WTF. 6 person company? So there's the CEO, the PA, your boss and you. That leaves 2 other spots. Unless the CEO is a complete idiot I don't see how the above statement is even possible as the CEO will know exactly what each of those people are bringing in.
My advice: stop over thinking this and stop reaching for more authority than you have and get on with the tasks assigned with you. You might want to do this quickly because a CEO is usually pretty good at sniffing out bad attitudes and will generally excise them to save the rest.
Of course, the above advice is assuming that anything you said is even remotely true. There are a lot of internal inconsistencies in the story you provided. For example the following:
He already tried just offering to organise the move himself but was
told not his role by the CEO.
This says to me that your manager likely knows why the move isn't happening and should be considered a clear warning to focus entirely on sales. There is a lot more going on here whether you know it or not. In a company that size I'd say finances is likely the real issue.