I have spent the night trying to move hosts....
1) backed up in full the database and site contents to local.
2) uploaded database to new host.
3) Upload site to new host, with new config file settings
4) changed nameservers at registrars, waited, site seemed to working fine.
Ok this is where it gets strange, i logged to try and check it had happened, so i thought a good way, would be to delete some plugins i dont need.
So i deleted two by logging into the new host with the new FTP details, refreshed, nothing happened in the plugins page.
So, i logged into the old server via ftp, deleted a different plugin, refreshed, and the plugin had been removed.
I phoned my technical support and they confirmed that the correct the domain was pointing at the correct IP etc. He was a friendly guy and said he had experience with wordpress but he was baffled what would do this, he checked my config file and it definately is pointing to the new server.
I cant believe it would make a difference but this is on a subdomain.
Any help would be greatly appreciated.