Magnificent, brilliant. Took me the best part of 24 hours to finish but it was worth it. I initially made 3 mistakes. Firstly I didn’t use 16 cubed because it started with 0, then I stupidly missed out 22 and 37 cubed, then, again stupidly, didn’t do 30 and 40 cubed thinking they’d be like 10 and 20. So, my message to any newcomers is “Read the preamble carefully”.
Incidentally, I cheated for the last stage. Once I’d got the first word and last three words I made an anagram of the remaining letters to get the key word. This made finishing the numeric bit a lot easier.