Well, any accent is fine as long as you speak clearly!
And on the question of 'British' accents... it depends what accent you mean! There are lots of regional accents (which can be spoken clearly) and there is 'BBC' English (which should be clear, but I do know people who mumble it!).
If you watch British TV you will often be listening too regional accents, bad grammar, and slang.
So, to improve your accent, to make it clearer, and more 'standard BBC' English, you should watch programmes which have these accents predominating.
Try some of the older British sitcoms (which can be bought on Amazon and come with subtitles). Try To the Manor Born, The Good Life, Keeping Up Appearances (listen to Hyacinth), Absolutely Fabulous.
Watch the Downton Abbey series (but listen to the difference between the posh 'upstairs' people, and those who work downstairs, in the kitchens).
Listen to BBCRadio 4, but you'll have no subtitles obviously!
You'll have to ASK a native speaker which accents are which.... as you might find it difficult to tell.
Watching TV is ONE WAY to familiarize yourself with the sounds of BBC English, or Received Pronunciation. But to imitate it will be much more difficult. Try getting a good pronunciation book, a mirror, and a recording device. Don't be afraid to make some really funny noises! And to pull horrible faces! It all helps to make the right sounds.
But speaking CLEARLY, and good grammar, is more important than accent. It really does not matter if your accent is Canadian, or Australian, or South African, or Scottish, or Welsh, or Indian or Nigerian..... as long as you speak clearly, and are articulate, and interesting!