[Neil Jones]

Possible they'll use 5-6am for signed content.   Looks like they currently do that 6-7am at weekends - not sure if there is a sign language requirement specific to the breakfast licence - most channels have to sign 5% of content IIRC.

There is:
www.ofcom.org.uk  - Page 48 - "The Licensee must ensure that at least 90 per cent of broadcast output which is not excluded is subtitled; 10 per cent is audio described; and 5 per cent is signed. The Licensee must achieve such interim targets for subtitling, sign language and audio description as are notified to him in writing by Ofcom or set out in the Code on Subtitling, Sign Language and Audio Description"