The couple who are buying our house came around at the weekend to look at some of the furniture we're offering for sale (heavily discounted). We've been very cautious up to now to not start putting any plans into action until we've exchanged contracts, because we know the house sale could fall through at any moment. However, their visit gave us a lot of confidence that the sale would go through ok; they were clearly very excited about the purchase, frustrated that things weren't moving any quicker, and agreed to purchase a number of items. So I think it's fair to say that we would be very unlucky if things fell through.
With that in mind, and taking into account what could be an extremely short period between exchanging contracts and moving out, we're not going to wait any longer - we're going to start selling items this week and we're going to start packing next weekend. We're still not going to book the flights until we exchange contracts though. It's not that I believe in tempting fate and all that malarkey, I'm just learning to be more risk averse - practising what I preach in my day job.