See the Dataset of Provenances for each artwork published by Collections Trust here:
https://docs.google.com/spreadsheets/d/e/2PACX-1vQ0HqOLC2dqJvDjASzgIzNAh125Ywz3WhA3YY1wSx-2-Cgk3en9eVNSj3xIzakG4SVZ0fPib4dw6WZQ/pubhtml
Download CSV: 14,916 provenances and questions about provenance gaps from the Spoliation Reports of UK Museums in CSV here
Consult the website of the Collections Trust UK Spoliation Reports for UK Museums