I assume that Graham will be back in September at the London Studios for the autumn run of the show. The studios won't close until the Spring of 2018, Graham usually goes on a Spring break around March for four weeks, so maybe this will be the time when he will host his last show from TLS
or he could decide Christmas 2017, as a new year, new start in a new studio could be reasonable.
Television Centre's Studio TC1 could be the new home for The Graham Norton Show. Jonathan Ross has decided not to bother with TLS when he returns this autumn, and so both shows could easily be produced from TC1. Graham usually but not always films his Friday show on the Thursday before airing, Jonathan was usually mid-week Tuesday/Wednesday.
Maybe Studio D at BBC Elstree is a bit too far out of central London for Graham, and Television Centre would be handy.