Average adult height in the UK today is around 5'6, maybe 5'7. So at 5'8 the OP is above average adult height. Particularly for a woman. Which the OP is.
It's a bit weird how many people in this thread seem to think that every adult is a man. You must all be aware that women exist.
Average height in the UK isn't increasing all that much any more. It dropped significantly during the industrial revolution due to the appalling drop in standards of living and resulting widespread malnutrition and disease, but that was restored by a couple of generations back. From the quick look I've had, average height in the UK doesn't seem to have increased between 1970 and ~2010 (the most recent large scale data I could find). Which would make sense since widespread childhood malnutrition and disease was already a thing of the past by then.
A few sample results:
https://www.bbc.co.uk/news/health-23896855
https://www.ox.ac.uk/news/2017-04-18-highs-and-lows-englishman’s-average-height-over-2000-years-0
https://en.wikipedia.org/wiki/Average_human_height_by_country
It's also worth noting that wealth was a major factor. The average height amongst people born into wealth probably hasn't changed very much in Britain the last 1000 years.