Wireless Networking/Video Sender interference

Waaauuggh!!  help!

We have a wireless router for sharing the broadband connection,   and I am now looking to use some wireless technology  to share  Cable & DVD sources  throughout the house.  The Cable box and DVD are both  wired  to the main TV,   but the structure of the house makes cabling a messy, and fussy  option .  As we opted for cable  purely to avoid replacing the roof mounted aerial,  it is now the only  source of broadcast signal in the house,  but I would like to add extra TV's  upstairs and in the bedroom.

 Initially I thought a 4 way sender  would be ideal,  with a couple of  extra recievers to allow multiple TV's,  but I read on the Maplins site that  none of the wireless sender  systems will work if  there is a wireless network present..??  can this be true??

If so,  is there a viable solution other than  having a DVD source with every TV, and paying for an additional Cable source??

 The ideal solution would allow for each TV to be able to view a  separate source..  ie  DVD in one room  and simultaneously DVD  in another  (Im happy for the cable source to  be the "same" channel at each TV!  I just want to relay the current program  when I am  working in different parts of the house for example)