In reply to Mord:
Is it Broadband dropouts or Wifi network dropouts?
If you aren't sure then connect one of your machines to the router with an ethernet cable - this will rule out the Wifi connection. If you're still getting problems, get on to Orange and get them to test your line etc. Don't just take "no" for an answer either.
If it's the wireless connection that is an issue, then there are lots of things that could be causing you problems. First step is to reboot your router, as you've said you will be doing.
I know you said it started when you got the printer, but that may be a coincidence (as unlikely as that sounds).
But, for now, turn the printer off and see if you still have issues. If not then I would suggest the next most likely expalanation is that somebody close by has set up a router operating on the same channel as yours.
You can check what channels have strong signals being broadcast on them by using Net-stumbler and then try changing the channel you use to another one.
Lots of good guides on the web for how to troubleshoot wifi dropouts etc - if that's what it turns out to be.
HTH
Si