If you do indeed want a refund, surely it's as clear cut as you paid them money to deliver a complete product by a certain date, assuming you bought in on the old TOS, they are now 18 months past that date.
I mean I'm no expert on UK law but surely it's that clear cut? So if you want a refund then regardless of what they tell you, you are in fact entitled to one?
Sure some people will accept the release date constantly being broken but I would have thought there's no requirement for you to do so. Within reason of course but c'mon, 18 months is a fair window.
The June 1st for me is a bit of a distraction, I mean sure it probably strengthens your claim but I would have thought you'd be entitled to a refund even if that wasn't there.
IANAL.
There's always Citizen's Advice, be honest with them though.
Also the
http://www.consumer-ombudsman.org/ who can probably help and will mediate on your behalf (I think it's free), but I would exhaust your options communicating with CIG yourself before going down that route. (would say avoid snipes in comms, keep it professional at straight forward).
I'd also say if you genuinely want a refund you're probably going to have to push a bit, lots of customers will just roll over so of course it's in CIG's interest to tell you they can't refund initially.
There's some more general info here :
http://www.moneysavingexpert.com/reclaim/small-claims-court
Not necessarily suggesting small claims court but more that link has lots of good general advice on how you probably should be dealing with this if getting a refund is your goal.
I'd also say about posting all discussion here, it might be a good idea, it might not I don't know, but I'm pretty sure CIG eyes will be on this thread given Derek's presence here.
Also try to ignore the "pledge" storyline, you bought a completed game to be delivered within a designate time window, you bought something, you didn't get it, and 18 months on you still haven't got it. CIG is not a charity, you paid VAT.