The days of the week took a different turn in England. In the 1st Century CE England was conquered by the Romans, with great difficulty. (Julius Caesar himself, who had successfully defeated the Gauls in what is now France, attempted to conquer England as well, but was forced back). Being under Roman control the people of England adopted the Roman calendar.
Rome left England in 410, however. With the sack of Rome by the Visigoths, the legions which had been occupying England for the past 3 centuries were more urgently needed in the homeland, and the Romans pulled out.
Left to itself, England continued to follow the 7 day week. However, at the end of the 5th Century and the 6th Century England was invaded, like the Roman Empire itself, by the Germans. In particular the tribes of the Anglos (From which England derives its name) and the Saxons. It is from these two tribes we get the term Anglo-Saxon.
Unlike the Germans who had taken control of what is now France, and Italy, and Spain, the Germans of England did not adopt the Latin language, or the Roman calendar. They did, however, accept the 7 day week, but not without their own changes. The Germans had their own gods, and these would become the basis for the names of the week.
The Germans attempted to find equivalencies between the Roman days of the week and words in their own language. dies solis and dies lunea easily became Sonntag and Montag. Tuesday became named after the German/Norse god Tyw, Wednesday after Woden, Thursday after Thor and Friday after the goddess Frigga. The only day of the week which remained intact was Saturday, for reasons which are not certain, perhaps because they could not find a god in their own mythology to match Saturn, the Roman god of the harvest. This leaves us with the weekdays as we have them now: