Hi,
Do you have the NHS app? I’m not sure if it will go back to 2009 but it might be worth checking before going to the GP to get a letter of them, which might charge you £20 or more.
I was in a similar position with my dyslexia diagnosis, from 2006, which the paperwork has completely vanished but I was able to get the same support from DSA with my ADHD diagnosis which I had the paperwork for.
A lot of conditions such mental health, dyslexia and ADHD will get the same support from DSA, so if you have paperwork for any other condition, it could be worth also submitting that as well, especially if your having troubles accessing your dyspraxia paperwork.
Have you spoken to the wellbeing or disability team at your university? They may also be able to support you with your application.
Hope this helps!
Suzan - Student Ambassador