update to WordPress 3.5.2 cannot be done via my admin on my liquid web account

I've had to set-up wordpress multisite manually on my liquid web account. I was hoping that after that I'd be good to update via the admin panel (1 click, or so)

but got the following message after trying to install it

Downloading update from http://wordpress.org/wordpress-3.5.2-partial-1.zip…

Unpacking the update…

Could not copy files.

Installation Failed

Is there something I need to do to .htaccess files or chmod settings of files and/folders to enable this to be easily done. Are there any direct instructions to issues that can help as I'm keen to do this without having to manually going through the process of downloading and setting up multisite all over again each time there is an update to the core wordpress software. Is there any particular server-side set-ups I should be asking from my service provider to have a more hassle-free set-up of wordpress. Are there lists of uk & US based hosting companies that provide more support for the issues faced by multisite users. This is something we have considered if our hosting cannot give the support or the tools to make this less hassle/ complicated/less disruptive. Or is this unavoidable ? As we're all in the same boat as multisite upgrading is as technical / laborious as the initial set-up.

Thanks for any help with this.
Darron
Bath Business Web