Whats the best/easiest/most effective method of creating 2 versions of the same app? I'd like one version to be free, with ad's; plus one version priced at tier 1 or 2, with no ads. Can i just do one project in BT, download, add in my sdk's and adverts, send it up to Apple, then send them the same but packaged with the adverts commented out? Or do i need to mess around with additional certificates? Cheers

You'll need two bundle id's. But it can be same project folder. Having the same folder means you only have to make future updates once, but it also means you have to change the bundle id and code for ads (and app name) every time you do an update. It's probably better to just have two project folders on your computer and probably two apps on your control panel.

I recently did this - one app in the control panel supporting ad-free and with-ad versions of the same app. Not too hard if you want to go with I-Ads. You create the app in BT, download it as a 'no-ad' version, compile in xcode to make sure it works as you expect. Then duplicate the project on your mac. Change the name and id for the second app, as that has to be different (necessary as it has a different name in the app store) and add the advertising. For the advert version with i-ad, I found the on/off test in each of the plugin codes where the banners should be and changed the code to make iad 'on'. Submit both to Apple and you have two apps managed from one entry in your control panel. Voila!

Hmm... There are no iAds options in my plugins anymore

Enabling I-Ad is a part of standard BT, I went down the easy route! But, the concept is still valid with other advertising, imho.

Another possibility is to use an In-App Purchase to remove the ads. I know it is possible, because I have seen it in Buzztouch-made apps, and there have been forum posts about it.