Top tip, get a USB lead (male a to female a (ie the same as the dongle plug and the PC Socket not a printer cable.) as long as you can (1.5m is about it IIRC due to signal loss on the cable related to this protocol).
Then if you find your room is in a 'black spot' you can raise your dongle with a bit of blue tack or just hang it out of the window. Miles better than balancing your laptop on the top of your wardrobe!!!!
USB max in the specs is 5m roughly IIRC. 4.8 works fine.
Avoid Orange, it is utter shit in all parts of camp (even with the extra T Mobile signal). O2 is OK and the popular choice.
There is WiFi in the 2 internet cafes in Old College, and New College aswell (might just be PCs in there, never tried wifi). No internet in the lines in Old College. There is internet in New College for when you get to Inters.
O2 is the best at Sandhurst, you even get reception over at Victory island. Worth getting a cheap pay as you go phone/sim to keep stashed in your room just in case your CSgt hangs onto your 'main' mobile during one of the obligatory d*ck arounds during Juniors. Also don't bother getting a dongle on a contract because as soon as you get to inters and New College you are forced to pay £15 a month for internet in your room, so you may as well use it.
As for internet, if you're not pluggin your ancient nokia into your laptop to use it's 9.8kbps modem, then you're not a real man...used to take me an hour to download a "small" picture. To find it was something dull my dad thought I would want to see!
In seriousness, I have always been orange in the and it never works well in military areas. Hanging out of the window to get signal was all part of the fun. But other providers have been as bad for other people - alot of the problem is the old buildings, well built and with free lead shielding in the paint and wall cavities...