>>13835663ROH means runs of homozygosity. These are stretches of DNA that are identical on both chromosomes. Large ROH usually means that the individual got the same DNA from both parents, meaning they are related within a few generations. ROH usually detects relatedness within the last 100-200 years.
FIS is another measure for homozygote genotype excess, but of the individual relative to the subpopulation. High FIS means that the subpopulation has a mating structure that results in parts of the population mainly breeding amongst one another. FIS detects longstanding population structures.
ROH for UK is very low, it can't be less than zero. FIS can be negative, zero is the "ideal" value within a population.
tl;dr: Brits aren't inbred in any measure.
