2 options. A cheap as chips digital dvd recorder that records on to dvd disks; or a pvr - that is a digital recorder that has a built in hard drive and functions like Sky+.
The disadvantage with using a recorder attached to a freeview box is you can only record what you are tuned to.
I highly recommend a Humax PVR which can record 2 channels simulataneously while you watch another, playback as you record something else or just time shift back a live broadcast. They are now very affordable particularly as a HD Freeview one is being released this year.