To search for grants Turn 2 us is excellent, particularly if you are looking for funding for a specific child. It's best to know as much as possible about the child's and family's circumstances including where parents might work or have worked in the past. There are some extremely specific charities going back centuries that are linked to certain trades and parishes:

https://www.turn2us.org.uk/

Thank you Kate for asking - I am following.

Ability Net lists many charities that support access to technology and software. I personally haven't tried any of them

Thank you everyone and Kate - I will look into these