If you have to cut corners you might want to avoid works graded at 8 by the ABRSM, but graded at higher levels in other syllabuses. Looking at the pianosyllabus.com site I see for example that Bach's Prelude and Fugue in A major BWV 888 is graded 8, but is also graded 9 or 10 in other syllabuses. Similarly with Chopin's Waltz in F major Op 34/3. On the flipside, the 3rd movement of Beethoven's Sonata Op 13 is graded 7 in a number of other syllabuses. I know these things are highly subjective but it might help your thinking re what to work on.