Yes I have read that Nest can be a real annoyance (fussy) 
Not to many devices and Keeping it simple, as I do with most things in life, I would ditch the BT HomeHub and use same BT hub SSID/Password (as you suggested) and just plug in Modem and ASUS router (pre configured) and away you go.
Are you able to configure ASUS router offline ?
FWIW: Our SKY box whenever I swap out routers and use same SSID / Password takes about half an hour and then re connects automatically, so hopefully Nest etc will be simular .
In a completely sane world, madness is the only freedom (J.G.Ballard).
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