If it's not here by then end of this month it's being cancelled.
Are you building any equity in your current car Chris, or did they just tie themselves to promising your cost to cgange woukdn't increase? Given the current climate, your current car may have actually appreciated if you were to sell independently.
they worked out a deal on a suspected delivery date and gave me a trade in based on that. I've since made two further payments so the extra will be added into the deal I suppose. Trade in price is fixed in but was specifically asked not to sell the car privately presumably so they slap 2k onto the trade in price 
£2k? And the rest! Bet the buggers give you nowt for the 2 payments made, claiming the car has depreciated by the same amount.
If you were to sell, there's nowt they could do about it. You might want to get in touch with the place I sold my R to, for £2k more than the best price offered at Pulman or Lookers - Prestige Performance Yorkshire. They requested pics and description, they came up on the train to appraise, pay electronically and take away within an hour . If you give a true statement of condition, they won't chip you down when they get to you.