I always found these trains elusive, but soon after DRS took over operation from EWS the service settled down to pass through Bangor eastbound at 12:00. On 7th May 1999 20 301/2 obligingly stopped at the signal so I could photograph it at leisure.
These trains run Tuesdays and Fridays as required - after a few weeks the timings reverted to the previous arrangement, leaving Valley soon after 15:00 and passing Bangor eastbound around 15:40. The westbound train normally passes Bangor around 08:40 but sometimes runs earlier.
Here's a close-up of 20 301
Former Hunslet Barclay locos 20 902 and 20 903, later to star in the Kosovo Train for Life, on 24th Aug 1999
20 310/2 pass Bangor signal box on 5th May 2000