[1.5.1.3] Remove "I want to use a new address" in checkout

I would like to remove the option of adding a new address in the checkout processes for registered users.

Anyone know how I can do this? It's in both Step 2 and Step 3, where you usually choose between:

"I want to use an existing address"
"I want to use a new address "

Thanks in advance.

Edit the /catalog/view/theme/your-theme-name/template/checkout/address.tpl file
Personally I would just put a <div> around it with style="display: none" to hide it, so as not to break anything else

Sounds great but ehm, I ain't the sharpest tool in the shed when it comes to coding so could you perhaps post the exact changes needed (what and where).

Also, if it's not a hassle, I would like to hide the radio button so it only is text left saying Choose Address.