Help me diagnose the penalty

[trooperbill]

Back in April everything was going fine with my site www.gmt.gb.com - around the 25th tho i lost all of my rankings. I haven't had a notice from Google about anything in webmaster tools and am pretty lost.

Can anyone help diagnose whats happened?

Its been 6 months now and here's what i've done so far without any success:

Backlinks:

• Downloaded all backlinks using Majestic SEO and manually reviewed each one.
• Ive contacted websites i think are of low quality asking for removal
• 6 months later ive re-run the report and disavowed each of the domains that remain.
  

Onsite:

• I went through the website and fixed as many of the w3c errors as possible
  
• I ran copyscape on every page and re-wrote everything that was highlighted
  
• I de-optimised all title tags
  
• Ive 301's all dead pages to relevant content
  
• ive noindexed and nofollowed all links and the folder containing PDF's
  

I've even bought Fiverr gigs that help diagnose penalty issues without any recovery.

The only remaining thing i can think of is that the site was moved to a cheaper USA host around the same time - maybe this is a bad host tho i have no way of checking. I also temporarily set the geolocation of the site in webmaster tools to the UK to see if it would improve rankings (its set back to global now).

Can anyone help me out - i'm at my witts end?

I'm in the process of rebuilding the site from scratch using new file names and intend to 302 the old content to see if this will help recover things - but this wont help if the home page has been hit.

Thanks

Mark