I have just booked for my wife and I to travel to DXB in January returning from HKG in February in Club World fare ex-LHR £6426. I first looked at from AMS and there was a fare of €4730, but it would have meant that we would have to go directly to AMS because of the 355 days in advance booking.
Left it a week and a bit and in the meantime the fare rose to €7920. I checked from BRU and the fare was €5259, but with shareholders discount this came down only to €5133.70. Even so a considerable saving over the fare ex-LHR and two seperate weekends in BRU.
VK is right about adhering to the fare rules, some years ago Eurotunnel were offering cheap day returns after 1300 at a third of the price of a standard single. A friend of our took one of these and drove down the coast returning via ferry to Portsmouth, but a few days later had his credit card debited for the difference in fare, quite legal, its in the rules.