Good on ya.
A few ex-squaddie mates are doing it. One of them tried to rope me in but it would quite literally be the death of me. The nearest I came to being a vet was giving eyedrops to the cat and the last time I saw service it was in Pizza Express. I therefore bought my way out of it by donating and sharing the post.
On Facebook there are quite a few 'text PTSD22 to xxxxx' messages; it looks like four of five charities have jumped on the bandwagon. Combat Stress as per your link are probably the best known and I would imagine a good place for funds to go.
Well done.