Yes, you should mimic a British accent. Your first impression should be correct choice for you. There are different types of accents and some would be considered too strong to be understood, but you probably won't gravitate to those. I recommend you watch all episodes of Peep Show on Hulu. The characters are English with a few Scots. The shots are mostly close ups so you can really study the mouth movements. The characters are very affected and therefore easy to mimic. You should be able to say "right" just like Jeremy or "turkey fucker" like Johnson from the first go.