Please talk me through the process of buying a new build!

[breakingthebank]

We've looked around a new build show home today and to our surprise we really like it. At the moment none of the houses in the style we like have been built on the site we like (we visited a show home on another site), they will only be building 3 of our style houses (1 has already been sold now) and they won't be ready until December. The developer isn't offering part exchange on this development.

I'm really confused about the process we'd have to go through to buy one of these new builds. Do I have to have a mortgage offer in principle before I can reserve a new build? What will I have to pay to reserve it? What happens about selling my current house - what happens if I sell it quickly, will I have to move into rental until new build is ready? I really am clueless about the whole process and I want to get a better understanding before I speak to the sales staff so that I don't look as green as grass! If anyone can talk me through it step by step (an idiots guide please) I'd really appreciate it.

Each builder will vary on their processes.
I think you will need to know if you can get a mortgage for the amount before they will let you reserve, although if they are a larger builder they will probably have mortgage advisers to send you to.
Reservations vary from £500 to a few thousand, check under what circumstances you could get it back.
Usually you'll be given a date when they expect you to move in by, or a date when they expect you to have a sale by.
They may not have part exchange, but they may have estate agents you have to use, they may value your property and agree a price you should sell for.
Anyway, each varies considerably, so bite the bullet and walk in!

I agree with Sunny it really depends on the developer. We have purchased three new builds and each has been different. The last one, we had to be proceedable even though the property wasn't going to be ready for 6 months, because we had to exchange in 28 days. The reservation fee was £500. We didn't have our AIP when we offered, we just told them we were proceedable. As soon as our offer was accepted we saw our mortgage advisor, however DH had already run it past our FA (she knows our finances well). Our build was delayed 6 months and we moved in 11 months after we exchanged.