Hi you can buy the clips on ebay, key in a search for tandem buggy they listed within that catagory cost less that £20

I'm a mom of three 6,4,1.  I love my E3.  It is the only thing I wanted or needed for baby #3.  I think the basic model would make the best first baby gift and the add the other seat. 

My Girls also love it.  don't tell anyone but at christmas i put all three of them in it.  I had the 6 year old hold the baby and I pushed them throught the mall.

I have to say that the best invention EVER is the Phil and Ted E3 

http://www.philandteds.com/cat.htm

 Look one up. It is a single and a double, for one baby and a toddler or two toddlers, depending on how you arrange the seats. I have had one for about 8 months now, and just wish I had known about the when I had my first because it is equally good as a single or a double. Basically, it is a single three-wheeler but instead of  side-by-side or one in front, it is more like a double decker. Because of this, it is still easy to take shopping, fits through all doors that a single would and is really manoeuverable. I love mine, as do all my friends who have one.

The one doubt that people have when they see one is whether the child below will be happy there. The answer is yes - they can still see out, feel like they are in a go-kart, and can easily see the person pushing.

They aren't the cheapest but for a double I would say without doubt the best! (Advert over, no comission made, unfortunately!)