Whew! That was a tough one - we've only just finished now! Sorry I've taken so long to respond - and to thank you. I'm amazed and impressed that you did it so quickly, Quisling.
We'd got three of the missing letter sets but thought they were always added at the beginning. Only today did we get the fourth letter set. In the end it was quite a slog. There was a lot of new vocabulary. We made heavy use of onelook and wikipedia!
Thank you so much for your help!