I haven't signed a lease agreement yet, only the initial order. But I have paid a deposit to the dealer, so that might give me some leverage.
They are definitely dragging their feet this morning! VWFS won't let me speak to them as the agreement isn't live yet. SEAT Customer Services don't want to know as it's a VWFS issue. Apparently my only choice is to go through the dealer, who are being helpful enough.
VWFS did let slip that the increase in price was because I will now be getting an upgraded MY19 model. Which obviously wasn't my choice! Would have been more than happy with the spec I ordered in March.
I have all the paperwork, including the original terms.
Still feeling livid. I expect this will be resolved one way or another today - either they honour the agreement, or I'm walking away and seeking compensation for the distress and inconvenience.