Crikey, you have painted yourself into a tight corner. And whatever watch you get, it will need servicing before wear as otherwise the dried-out works will grind themselves up. That will cost anywhere up to £200 for an auto, £120-ish for a manual wind and there's no way to get that done in time for the 15th.
This manual Omega looks honest to me and has a serial number that according to the tables dates from 1958. The photos are poor and you'd have to ditch that bracelet, but the dial isn't bad, the movement looks clean and it has the original box. It ends in 4 days so it'd be a gamble but I would be surprised if it goes above £500, but it's 9ct gold so you never know. However I doubt the first one you linked to will exactly fly out in the next four days but again, that's a gamble.
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