The top one was much paler (quite silvery) smaller than the lower one which was larger and darker.
I've never seen Scarce Silver Y - which in any case would seem to be out of season anyway but always worth a check. (?)
c 15 mm
Also this morning...
Common Marbled Carpet x 3 together - and all pretty worn
November Moth agg x 5
Blair's Shoulder-knot x 1
Light-brown Apple-moth x 4
Tachystola acroxantha x 1