Here's some information from my colleagues from @LasaICT
Assisted Digital is a fairly worthy initiative, with its main focus being to ensure accessibility of government web services through a unified set of standards and end user testing, etc. There ia also a variety of web standards (W3C and BS 8878:2009) to guide web designers. The DDA covers the provision of services to the disabled, but is not specific on the question of web services.
Also, research from people like Abilitynet shows that awareness of disabled customers and accessible web design tends to be fairly low amongst those commissioning websites - usually folks from marketing and comms - and if accessibility doesn't get asked for, it doesn't get done. However, none of that answers the question of driving channel shift to actually getting disabled people online.
As to what's out there in terms of assistance to get online, there doesn't seem to be anything joined or coherent. Abilitynet did have a funded scheme which loaned disabled folks accessible computer kit to try out, but funding ran out some time ago. DigitalUnite does home tutoring, but this is predicated on the punter's ability to pay.
The only digital by default target we've seen relates to 80% of JSA claimants to be done online by 2013. Does this mean people will now skype their Jobcentre instead of turning up in person? HMRC is probably the best example of digital by default. There is a telephone helpdesk, but beyond that all official interactions with HMRC have to be done online - postal returns are liable to a fine! This impacts on disabled people in receipt of direct payments (which effectively turns them into small employers), forcing them to engage solely online.
You can also find a recent article we did looking at similar issues here ictknowledgebase.org.uk