Basically in 2005 Toonami UK stopped airing original Dragon Ball early in the year, Dragon Ball Z ceased to feature in regular reruns around the spring time at which point Dragon Ball GT had one more complete rerun that ended in the summer.
That said episodes of the series were featured in a marathon Toonami held. I did some digging and found the following schedule from a TV guide published the week of August 27th-September 2nd that year:
Does anyone remember this marathon? It is interesting the Dragon Ball Z listing from 7am-9am has the subtitle "Animated Adventures" whereas from 9am-10:30am it is just Dragon Ball Z. Were the movies rerun at this time? Are the Dragon Ball and Dragon Ball GT listings for the series or the movies and GT special?Sunday, September 2nd 2005
7am-9am : Dragonball Z : Animated Adventures
9am-10:30am : Dragonball Z
10:30am-1pm Dragonball
1pm-2pm : Dragonball GT
2pm-3:30pm : Dragonball