Cutting DVB subtitles to match cut ES

[Palmnut]

I record UK DVB-T directly using a Nebula Electronics card. I parse the recorded PVA streams into audio and video files using Project X. I then cut these files using MPEG2Schnitt to remove unwanted material before and after the programs and in the ad breaks.

What I am now wondering is how I can cut the subs, extracted to either SRT or SSA format, to match the cut video/audio.

Any help welcome please.