I'm afraid I can't accept manuscripts or illustrations for advice, as I have started to receive too many, and much as I love seeing them, I spend more time emailing than actually working! I hope you understand.
But here is some, hopefully, helpful advice for would be writers and illustrators:
I used to teach on the MA in illustrating for Children at Anglia Ruskin University in Cambridge. It is a wonderful course, and Professor Martin Salisbury, who is the course leader, has written a few books about illustrating for children. One of my favourites is 'Illustrating Children's Books'. It is a treasure trove of useful and enjoyable advice for anyone interested in writing and illustrating for children. It explains everything, from where ideas come from, to how to get published. It's worth it's weight in gold!
My friend Juliet Claire Bell writes a wonderful blog all about the life of a writer, and the process of making a book and getting published. It is a great blog, very funny, and full of good advice. She wrote a piece called, 'Increasing the Chance of your Picture Book being Published', and another one called, 'How *Not* to Write a Rhyming Picture Book'. Both very honest and funny, and full of valuable advice. She will even read your manuscript and give you some advice for a small fee.
'Words and Pictures' by Quentin Blake is a brilliant book, one of my all time favourites. It's not a guide to writing and illustrating, but it gives a brilliant insight into the creative process and should get any would be writers or illustrators going. Sadly it's out of print, but maybe you could get it second hand, or borrow it from your local library? I've looked at my copy so many times, it is falling apart!
A trip to Seven Stories is a good idea. This is how they describe themselves:
'Britain's national gallery and archive that celebrates the wonderful world of children's books.'
They have fantastic exhibitions for adults and children, often displaying original manuscripts and artwork and letters between publishers and authors and illustrators. It gives an wonderful insight into the world of children's books. Well worth a visit! I feel renewed with excitement and inspiration every time I go.
Hope this helps, and good luck!