If you prefer to use BSL to apply for renewal, you can. Go the .gov AtW renewal page, and look down the page until you see "British Sign Language (BSL) video relay service" (see picture below), then click on the "go to video relay service" link.
If you need to renew and you have a change in circumstances (e.g. you have new things you have to do for work, or want to change the communication support you need, etc.) then AtW will first check if you are a Key Worker (e.g. you work in the NHS). If you are a Key Worker AtW will try to sort out your renewal as a priority. If you aren't a Key Worker, then AtW will sort out your reconsideration and change of circumstances request as soon as they can.
This information has been checked with AtW.
Originally the extension to the award was for three months, but is now for six months. AtW have also said they will prioritise (try to to deal with as quickly as possible) Key Worker Renewal requests when there is also a change in circumstances. This update has been changed to reflect this information.