I found my AncestryDNA ethnicity results to be reasonably accurate, if I allow for a plus or minus 5% margin of error. When I compared those results with the known ethnic background of my ancestors, AncestryDNA was more accurate than other companies I have tested with. I have complete information for the most recent five generations of my ancestors, and almost complete information for six and seven generations (back to the mid-18th century).
I have five different ethnicities, with none in the majority. The main ethnicity not identified by AncestryDNA was the Breton French ancestry of my great-grandfather who was born, as it happens, in Jersey. His parents, grandparents and great-grandparents were all born in Cote d'Armor, Brittany. Because of the Breton connection with British Celts, possibly some of his contribution to my DNA was classified as Scottish or Irish. Some of his cousins still live in Guernsey, and I presume there is significant French ancestry in Guernsey, as well as ancestry of UK origin.
To assess the accuracy of your results, I suggest comparing them with the known ethnic background of your ancestors. Were all of your grandparents and great-grandparents born in Guernsey? If you're not sure, it should be possible to find out using Ancestry's search tools.
As for looks, the only thing I would expect from your ethnicity results is that you probably have light skin. I wouldn't expect any particular eye colour, hair colour, straight or curly hair, height, long headed or round headed. Those ethnicities have a diversity of looks.
Of other companies I have tested with, 23andMe also gave me reasonably accurate ethnicity results, including some accurate Irish and English results at the county level. MyHeritage, FTDNA, MyTrueAncestry and GenomeLink were less accurate. MyHeritage, for example, said I had 13% East European ethnicity. Apart from this being inconsistent with the other companies' results, their is no indication of this ancestry in my known genealogy.
In summary, I suggest treating ethnicity results from any DNA test as indicative rather than definitive.