Platform sgns policy seems to be as follows:

Willesden Junction - black-on-white LO "temporary signs" (no LO
oundel).

Queen's Park to Harrow & Wealdstone (except WJ) - mainly temporary
sheet metal or self-adhesive square LU red & blue roundel signs, plus
some linier ex-STS "banner" signs at H&W adapted to carry station name
+ separate LU roundel.

Gunnersbury, and Kew Gardens - ex-STS linier "banner" signs at H&W
adapted to carry station name blue-on-white + separate LU roundel.

Blackhorse Road, Highbury & Islington and West Brompton, ex-STS
platforms now under LU control but served by LO - ex-STS "banner"
linier signs adapted to carry station name white-on-orange + separate
LO roundel.

All other GobLin and NLL platforms retain various Silverlink-era
signs, some linier, some rectangular, some still with green & blue
lower STS flash, others at Gospel Oak and west thereof with a green
border.

What's the situation at Olympia and north of H&W?