The Wellcome Trust Screenwriting Prize is an annual prize that aims to encourage the creation of high-quality feature films inspired by biology or medicine.

http://www.wellcome.ac.uk/Funding/Public-engagement/Screenwriting-Prize-2012/wtdv033928.htm

Looked good... but on closer inspection:

'The Wellcome Trust Screenwriting Prize 2012 is open to writers who can demonstrate a professional writing credit in the following areas:
a) television (drama or narrative documentary): a screen credit as a writer
b) film: a screen credit as a writer OR a commissioned screenplay for which you were paid
c) theatre: a professionally produced play for which you were the writer
d) novel: the writer of prose fiction, excluding self-published books.'

Also...

'We are looking for writers who can demonstrate they have written a long-form piece, so you are not eligible to enter if you have only written for a short.'

Looks very interesting. I'll certainly pitch an idea to them.