I have an Ocean on order from Eurovans Crawley via DtD. They are hopeless communicators (but to be fair to them, the factory practices dark programming arts) but it is worth 9% to me. Essentially all my options were 'free'.
When I call them they do answer, but they never call me. Others on this forum suggest you may (by luck) receive your order quicker from non-DtD dealers (for quota reasons). I doubt that, as have seen orders coming through Eurovans much quicker than mine, so suspect mine is held up (10 months since order) because of spec shortages.
Whoever you use, get your order in, get and order number from the dealer (essentially proving the order has been accepted by the factory), get in the queue, and then scour the options list again, you can change options until you have a provisional build week. I respectfully suggest you may have overlooked the larger fuel tank for £80 for instance. Many do, but why wouldn't you add it? (unless you're getting a 4motion when, ironically given it is thirstier, you can't add it for weight reasons!).
I've rattled on enough. Enjoy the anticipation.