The Vikings were from Scandinavia which is north of England. It was a short distance to travel on a raiding party. The raiding parties saw the fertile croplands and bountiful harvests produced on English soils. The raiders also saw how little trouble they had being successful in raids against the Saxons, Angles etc...So the Viking Age in England began in ernest around 710 AD and ended in 1066 after the Battle of Hastings.
As I said earlier, distance was a great factor in the Vikings choice of England. The Hebrides (northern British islands) are only about 2 days sailing from Scandinavia. Evidently the Vikings used these islands as far back as the 10th Century for keeping treasure and making burial cairns. The raids took them further and further south on travels of exploration and conquest.
Another huge factor in choosing England over other places was the climate. England is made temperate by the Gulf Stream. The water around England is liquid all of the time, and the climate is much milder as a result of the warm ocean current flowing north from the tropics. The result is that the growing season for crops is extended and the climate is not as harsh as that experienced in Scandinavia.
Since the Vikings were a waring people, they were practiced in fighting and showed no mercy when raiding. "King Alfred and King Guthrum in AD 880. This was written as follows: Up the Thames, and then up the Lea, and along the Lea to its source, then in a straight line to Bedford, then up the Ouse to the Watling Street." (http://www.jorvik-viking-centre.co.uk/vikings4.htm) Place name studies show that Vikings named town areas ending in -by (meaning settlement) or -ir (meaning farm) in areas of the Danelaw and in upper Scotland.
The Scandinavian people have a rich oral tradition of Sagas (epic tales) by which great people were remembered. It is through this literary tradition that the Orkney people's Saga and the Saga of Egil Skallagrimsson came to be preserved and discovered by modern literary scholars. (http://www.mnh.si.edu/vikings/start.html)