Thankyou for all your replies.
I did say I want a pair of panniers that are "as big as possible for long-distance touring", not for my bike "to win a beauty contest". As such I will take Paul2bikes' advice, as Sw Motech Adventure panniers seem to be (a) the biggest and (b) well-appointed for securing additional luggage on top!
I could do with a new tank bag too, as the Tiger 1050 tank is a very different shape from those of my earlier bikes, so none of my old tank bags fits very well. A tank bag that can be expanded would be nice. Any recommendations?