After all of DBZ getting released in the UK on DVD Manga UK have now released the first Season of GT and are releasing Season 2 in March. Dragonball GT is a series which, in my opinion, doesn't get the credit it deserves. I'll admit things don't start out that amazingly but the series picks up after a while and really hits its stride. When GT first started they tried to take it in the direction of the early episodes of the original Dragonball series aka a fun adventure searching for the Dragonballs. While this direction worked great in the original Dragonball and made for some great entertainment, it doesn't really work in GT because the characters are all so powerful and shouldn't really be having any trouble.
Fortunately the makers soon abandoned this direction and went full-on DBZ style with it instead with plenty of action and epic transformations. I'd say this change occurs around the half way mark through Season 1. It's definitely worth sitting through though as things do get great and even better in Season 2 which comes out in March. GT only has 64 episodes which is only 2 Seasons so if you've already bought all of DBZ this isn't that much to buy. Also Season 2 will include the GT movie.
When GT aired in the UK it was made hard to watch largely because the voice cast was the Blue Water dub cast instead of the superior Funimation cast from DBZ. This release uses the Funimation voice cast and is fully uncut and I must say I'm enjoying it a lot more than I did back in the day as a result. Like with DBZ it contains 3 audio options:
English with Japanese music (which is the default) English with English music Full Japanese
With DBZ I always recommended watching with English music. With GT however I would say either music option is good so try both and decide which you prefer. And there are some really good English covers of the Japanese intro/ending themes if you watch in English.
Now I'll get to the story. Goku gets turned back into a kid by the Blackstar Dragonballs and is forced to travel the universe with Trunks and Pan in order to collect them all to prevent the earth from being destroyed. There are some good fights here and there at first like Goku vs Legic, Goku and Trunks vs Lord Luud and Goku vs General Rildo. But things really pick up when the first major villain Baby shows up and starts possing people and powering himself up. At first he isn't that much of a threat but when he escapes to earth with Goku and co. still in space we get to see Goten, Gohan and Vegeta each fight against him and end up being possessed.
When Goku and co. return to earth they realise that the entire planet has been possessed and must fight all their friends. Eventually the only people left unpossessed are Goku, Pan, Mr Satan, Majin Buu and Uub. Goku fights Baby(who is in Vegeta's body controlling him) at Super Saiyan 3 but can't maintain the form for long in his Kid sized body. He ends up losing to Baby who transforms twice in the process. Goku gets Old Kai to help him regrow his tail while Uub merges with Majin Buu to become Majuub and fights Baby himself before losing. Then Goku returns and fights Baby again at Super Saiyan 3 but loses again only to transform into his Golden Great Ape form and gain the upper hand while losing control of himself. Right at the end of this Season Pan manages to bring Goku back to his senses which causes him to transform to the all new Super Saiyan 4 which sets the stage perfectly for Season 2. It's also interesting to note that Goku is an adult again while in Super Saiyan 4.
Overall if you enjoyed DBZ then you should at least give GT a chance. Even though the start isn't great and it is the least best of the Dragonball trilogy(DB, DBZ and DBGT) it really isn't nearly as bad as some people like to say and really does get way better once it gets more like DBZ. Also Manga UK have confirmed that they'll be releasing the original Dragonball series after GT so keep a look out for that.