Presumably you are recording from Freeview? The .ts files are MPEG2 transport streams which are already encoded at source and only need a few adjustments to give you a DVD-Video. The key thing is to avoid any major re-encoding during these small changes, since the video quality is very good already.
To answer your question directly, the .ts file can be imported into MPEG Video Wizard or VideoRedo (both have a month's free trial), which can edit out preamble and advertisement sections, and keep the main video that you require. Only a few video frames either side of the editing points will be altered.
If it is Freeview transmission that you are recording, then the group-of-pictures (GOP) length is sometimes as much as 40 frames, whereas the interval appropriate to DVD-Video is 15 frames. Both MPEG Video Wizard and VideoRedo have options to save the files with these extra adjustments made, and thus make it easier to finally author a DVD.
To be honest, ConvertXtoDVD is a general purpose application and in this case may not get you the best quality with the finished product. If you process the .ts files as described above then you can author them to DVD using a freeware program such as DVD Styler.