1. IIRC it was at the Synod of Whitby that the Church of England decided to follow the Latin form of Christianity abandoning the Celtic form introduced from Ireland. In this ATL, the Church of England goes Celtic.
2. Lets assume that this isn't butterflied away by the above: Hastings, 1066. The Anglo-Saxon fyrd refused to be lured out of its Shield-Wall by the Norman knights' false retreat. The battle lasts until nightfall before both sides take a break. William the Bastard is still pinned on the Hastings peninsula with his back to the sea. The wily Harold plans and executes a dawn attack - taken by surprise, the Normans panic and run, abandoning their supply wagons and falling back to the beaches. Through a stroke of good fortune William doesn't make it - he makes a valiant last stand with a few unlucky or loyal retainers before falling beneath the Anglo-Saxon axemen of Harold's personal guard. With their lord dead, the Norman organisation falls apart - the invasion of England has failed.
The Engliscgreord (English language) would continue to be a literary tongue throughout the Middle Ages- OTL we had to wait until Chaucer's time before we got much literature in Englysshe. We'd get more epics along the lines of Beowulf. English would be a harder language to learn, probably retaining more cases and inflections and grammatical gender. It would be a more purely Germanic language unlike OTL where its got quite a bit of French mixed in. The Anglo-Saxon class system was somewhat more egalitarian than its Norman successor (where the Normans were on top and everyone else was on the bottom) so we might see quicker steps towards parliamentary government in some form (the Anglo-Saxon ealdormenn were very big on councils to advise the king).
I'm a bit hazy here - only thing I can think of is that without possessions in Normandy there are a lot less continental field trips for the English. The French will not learn to fear the mighty Welsh longbows. Possibly the kingdom of England (with its capital at Winchester? I'm not sure about this, was Harold's capital at London?) will be more interested in facing off against its historical enemies and kin, the Deniscan (Danes, Vikings). Scandinavia may be the area of choice for English ambitions. Maybe a Kingdom of the North would be the final result stretching from Ireland to Finland.