This is a variant or alternate edition of Willan's Te Lucis settings, focusing on refined contrapuntal interaction. The writing is idiomatic to the late-Romantic organ tradition and requires careful coloristic control on the piano.
At Henle 4 this is an intermediate piece that expects secure technique and real attention to phrasing. The main demands: independent voices that must each sing on their own line; a true singing tone, with the melody floating above the accompaniment; and chord voicing — bringing out one note inside a handful of others.
Focus on the independence of the inner lines to avoid muddy textures.
Comparable difficulty and character — good candidates for what to learn next.
A level or two down with the same spirit — ideal if this piece is still out of reach.
Where this piece's skills lead: slightly harder works making similar technical demands.
Chorale-Prelude on "Te Lucis" is rated Henle level 4 of 9 — intermediate repertoire, roughly ABRSM grades 5–6. In the RCM system it corresponds to about level 6.
You should be comfortable at Henle level 4 — meaning you can already play level 3–4 pieces cleanly. Learning it one level early is possible as a stretch piece, but more than that usually leads to months of frustration.
A typical performance of Chorale-Prelude on "Te Lucis" lasts about 3 minutes.
Chorale-Prelude on "Te Lucis" is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.
Pieces at a comparable difficulty and character include Chorale-Prelude No.1 - Puer nobis nascitur by Healey Willan, Chorale-Prelude No.2 – Andernach by Healey Willan, Chorale-Prelude on "Te Lucis", HWC 163 by Healey Willan — see the full similar-pieces list on this page.