Hi sweetpea
I can't say whether you should or shouldn't send in a pain chart showing where your pain is - but I would say be careful how you mark it. I think it is all too easy for someone who may not have knowledge of your condition to misinterpret what you mark and assume you can do things - because you haven't marked part of the body as a specific pain area,.
Regarding the GPs letter - it is fine to include it from 2018.
BIS
Nothing on this board constitutes legal advice - always consult a professional about specific problems