So far, I am not aware of any DVD recorders that can record subtitles unless the freeview box is capable of displaying the subtitles embedded in the picture. Unfortunately, in this case there is no way of actually turning off the subtitles in the recording since the subtitles will effectively be 'burned' into the picture.
A good majority of new DVD recorders on the market play DivX and XviD files. As most manufacturers are keen on advertising their DivX and XviD playback capabilities, if the recorder you see does not mention DivX/XviD support, then it mostly likely does not offer this capability. If you plan on watching DivX content, particularly Pay-per-view downloadable programming, make sure the DVD player is DivX certified. Virtually all DVD recorders offer MP3 support and as the soundtrack of most XviD and DivX files is encoded in MP3, any DVD recorder or player that offers XviD or DivX support will play MP3 files.
The last option actually depends on your freeview box. If the freeview box is just a basic model with only a TV-Scart output, then the viewer can only watch the freeview channel being recorded. For freeview boxes with two Scart outputs (TV + VCR), the VCR output should be connected to the DVD recorder. However, even these may only decode a single channel between the TV and VCR outputs. The manual or specification for your freeview box will mention if it offers this capability.
As I am maily familiar with Lite-On DVD recorders, these are the only models I can give suggestions for. For example, The LVW-1105HC+ features DivX, Xvid & MP3 playback. The Lite-On LVW-5025GHC+ features the same along with an 80GB HDD (for Timeshifting & HD recording) and a stereo TV tuner (at least the UK model).