Hi every time I try to load via extension manager I get 'Unable to find install package'. Any idea's please?

I believe you haven't changed anything that has to do with the zip filename, right?
The zip file is named plg_jw_allvideos-v3.1_j1.5 and inside you see the folder jw_allvideos and 3 files named en-GB.plg_content_jw_allvideos.ini, jw_allvideos.php and jw_allvideos.xml.
Right?

Yes that is correct.

The above has the file attached. Also tried loading from a directory and I get the same. :(

Are you sure that you have permissions to your server to install those packages?
The temp folder to the root of your site is writable?
The problem just occured with this plugin or you have it before with some other installation package?

No its not your problem I cant install any plug or com etc. Sorry not your fault...since installing 1.5.14 I have a prob!