Andrew,
AIP GEN 3.4-13 para 4.5.3:
ATS: "(Aircraft call sign) behind A340 on short final line up RWY xx behind."
You: "Behind the A340 lining up RWY xx (aircraft call sign)."
GEN 3.4 is devoted to comms and phraseologies worth a look as you might find it interesting like I.
"Over and out!"
