Welcome to the wait list (and the forums!). Great choice of colour (though I'm biased).
If your dealer is being a little slow to give you updates you can pester Seat directly - you can either use a webform (link: http://www.seat.co.uk/contact-us.html) which may or may not get a rapid response, or call them directly - number for UK:
New & Current Customers - 08 08 5 222 222
Mon - Fri 8.30 - 17.30
12-16 weeks is about right time frame, if you ordered beginning of May then end of August is a good bet, unless you chose some exotic options (ok... the Tow Bar is the main culprit although Seat customer services keep contradicting themselves on that one). The factory shuts down end of July for a summer break so if it's not built by end of July (so arriving mid-late August) then you'll likely see it manufactured end of August (and arrive end of Sept; with a '67 plate bonus).