No CITV didn't like it because it got darker, they were afraid they were airing programmes which were getting too dark for children, so they adopted a new policy not to air shows that 'they' think were too dark.
The UK didn't see the series properly till it came out on DVD in 2005.
It was intended for families and younger audiences. So some of the plots had to be watered down (no pun intended) because of that, plus original stories had to be made to fill in gaps where the stories from the book wouldn't have done the job well. By series 3, it got darker to try and attract fans of the book and film, but it wasen't aired in the UK due to those changes.
I loved the film, didn't know there was a series. I read the book last year too, it's very good and has a lot of nice detail. I really like the drawing, I think you executed Bigwig's character pretty well c:
OK? The TV series was made because Martin Rosen; the director of the film, wanted to make a TV series eqivelent aimed at families so more people can enjoy it. The series was also supposed to sell merchandise which some of the proceeds going to the estate of Richard Adams.
The beginning of the series did try to stay true to the book, but taking a few liberities along the way. But after the introduction of Efrafa, the series did become more reliant on original stories, though it's rumoured one or two stories from Adam's 'Tales from Watership Down' inspired a couple of stories.
In Series 3, they did give us more of a backstory for Woundwort which neither book, nor film had acomplished before and gave a minor character, more of a major role.
At the end of the day there are both positives and negatives that the TV series had brought on.