I've only just found this thread.

I thought this was a very good programme, largely because of Philip Langridge's enthusiasm. It seemed surprising, considering how often he's sung Peter Grimes, that he'd never seen the composition sketch before. He seemed quite overwhelmed with excitement ("It's my life!"). It was interesting for me to hear all the comments, because I have a facsimile of the sketch and could look up all the things they mentioned. For  a long time I thought all the splodges on it were coffee stains made by the over-excited composer, but it seems they are stains from a leaking pipe in Reginald Goodall's house! Of course, I realise now that Britten was far too meticulous to spill coffee on his writings. It is very exciting to see the way the notes sometimes just fly from the pencil, sometimes there is more of a struggle, and to see how the words differ in places from the final version - for instance the famous words that are now on Maggie Hambling's sculpture at Aldeburgh, "I hear those voices that will not be drowned", do not exist in this draft.

It's frustrating that the actual complete manuscript pf Grimes is in Washington - it was, after all, an American commission from Koussevitsky.