All of our uPVC French windows are internally-beaded. Having internal beading is perfect for anyone installing their new windows, as you can fit the 28mm sealed unit from inside your house. The alternative involves you having to balance the glazed unit while you carefully navigate a ladder. Once you are at the top of the ladder, you then have to negotiate the beading into place before hammering it in place securing the glass. Not only is this a far more dangerous, and complicated, option but you will be outside exposed to the elements.
Another benefit to having internally-beaded windows is the added security. This may seem like a simple feature but there are still some companies which sell externally beaded windows. Having the beading on the inside restricts the opportunity of easily removal from the outside, by preventing burglars from taking the sealed unit out of its window frame and gaining access to your property and your valuables.