You don't need any dedicated phone line to get broadband.
If the modem-router is provided by Orange, it should be fully compatible with the protocol they use.
Most router, from most makers, are roughly equivalent when used at home. Most slowdowns are not router related.
You only need the broadband modem, and optionaly a router. Having a router makes things safer as it will hide your computer from a casual hacker, but only when using a cabled connection, and hides the ports that you use, hiding the router itself.
Things that can slow you down:
The whiring between the phone entry and the modem is to long, or goes through some extention. Make the whiring as short as possible.
Line noise. When using the phone, is the connection noisy? That noise can also degrade your speed.
Look if you can find some obvious interferences sources. Look if you can move them or place a metal mesh between it and your telephon whirings. You may need to call a thecnician to do some trouble shooting and apply some correctif.
To many devices connected to your line. More than 3 phones, an answering machine and an alarm can look good, but can realy impare your internet connection.
How far is the router from your computer? How many walls or other separation between the router and the computer? It can be very important if using whireless in your home. It may be advisable to use an ethernet cable to connect a stationary computer like a desktop.
Check if there is any channel conflict between your network and that of your neibours.
When using a whireless router, you should NEVER EVER suppress the beacon. Contrary to the legend, it can actualy make your whireless network LESS SECURE. The reason is that in this case, your computer must broadcast, in plain and uncrypted text, it's credentials. This allow anybody to sniff your credentials and connect as if using your computer to your network, of impersonate your network in any other location if you use a portable outside.
The intruder no longer detect the router, he will detect any device comunicating with it and can now pass as either your router to your computer OR as your computer to your router.
It can also make your connection slower.
Electro, July 2012