Extensive disruption on Friday 2nd October due to one or more signalling problems between Warminster and Salisbury. Described on Journeycheck as a signalling problem, there was a message that one fault had been fixed but that another was still causing problems. Audible announcements suggested a level crossing problem (and Wylye crossing was the location at which some rail staff were seen at the lineside cabinets and / or armed with flags).

Whatever the exact cause, the result was:
 

• Fault manifest by 11:15, with 1F11, the 09:28 from Cardiff, being delayed by 65 minutes at Wylye and 80 late at Salisbury
• Cancellation of Bristol-Salisbury and vv. services between Westbury and Salisbury
• Subsequent Portsmouth services in both directions being heavily delayed, and running under caution for significant distances, with delays around 30-90 minutes.
• Services stopping short of destination (3 failed to reach Cardiff and 6 stopped short of Portsmouth)
• Some stop-skipping to make up time (or, as suggested by onboard staff, as a response to overcrowding)
  

The problem was rectified by around 20:30.

I don't know of any advice for Dilton Marsh passengers. The first cancellation on your list, the 2O10, was, if I recall correctly, due to "more trains than usual ..." and not connected with the signalling problem. It was the train that I had intended to catch.