Anyway there are two things that are really concerning me, one his beak? It's split and incredibly overgrown - one side has continued to grow upwards while the other side hasn't. Secondly he is very very scaley and has a lot of flaking skin.

He is in a Luke warm bath as I write this, to see if this can help with his skin. I will be booking him in at the vets to have his beak checked this week ( luckily one of your recommended vets is quite close to me). What I want to know really is this something anyone has seen before, is it quite easily fixed or is the damage too much now? I imagine this has happened through years of neglect rather than months. 

You are right, it's long term neglect. It is in a disgraceful state, the vet will also assess if there are other problems. In the absence of disease, the are resilient, so it should improve. Book the vet asap.

Re. species - a pic of it's shell is needed to confirm this.

If you also send pics of your setup, I can advise if it's satisfactory.

Tom