A dedicated computer monitor, no, you can't watch freeview on it because dedicated PC monitors has no SCART or RF input which a freeview set-top box needs to get the freeview signal, EPG, & OSD menu to the screen.
Your best option is to buy a dual-purpose TV/PC monitor. They can be used as a PC monitor or for watching Freeview (some even have Freeview built-in so you don't need a set top box anyway). Really depends on how much you are prepared to spend.