have an EE femtocell. I got one when they were first released on the 10th of December 2012. I have heard that they are not available at present because the second batch delivered was faulty. The rumour is that the next batch is due very soon. Once stocks are up to speed they will be available to everyone.
It is the same femto as the "3" version and is very good. Highly recommended. At present you dont need to register numbers so anyone with an EE/Orange or T-Mobile 3G phone can use it. I think that is to change though. With regard to the interference I am sure if you used a long ethernet cable and put some space between the boxes they would all be fine. Seems strange that EE wouldnt let you guys ave one.