The GBP 6M Libor swap curve will now use the fallback securities for 1M and 6M rates as the old securities are no longer published as of the end of March due to the LIBOR cessation. Please refer to the security changes below
Old:
1M Libor = BP0001M Index
6M Libor = BP0006M Index
New:
1M Libor = VBP0001M Index
6M Libor = VBP0006M Index