Shay,
There’s no easy way to mark a gaming site as a UK brand. A site’s reputation is built through being established and trusted in a certain territory for a good number of years.
At risk of laying this on a bit thick, Sun Bingo, Jackpot Joy, and News of the World Bingo (promoted through Market-ace) are the most popular household names in UK gaming because they have built up a loyal following through fairness and reputable dealing.
Being UK focused is the same as being trusted by UK players. Simple.