Two battles a few years apart turned the tide of history against Christendom for a time. In 717, Caliph Suleiman's reinforcements reached the walls of Constantinople* and broke the stalemate, capturing the city and crippling the Eastern Roman Empire. Four years later, the Wali of Al-Andalus captured Toulouse, allowing the conquest of Aquitaine, an autonomous nominal possession of the Frankish King. The next year, the King of the Franks, Charles Martel, attempted to recapture Toulouse and was killed in battle. The fragile kingdom fell apart into bickering petty states, allowing the Muslims to piece by piece conquer Francia from the west while establishing dominance over the Balkans from the east. While the overstretched Umayyad Caliphate would soon fall and the Berbers of North Africa who made up the bulk of the Caliphate's armies revolt, Muslim successor states had taken root in Europe, and by the end of the 9th century the situation had stabilized and new polities were again leading the Muslim advance into Europe, despite their gains having been eroded somewhat in the meantime.
While it was often difficult to secure gains in Francia and Italy, the Sufi orders who traversed north found a more pliable audience in the Norse and Slavic peoples; still holding to their old pagan beliefs, in contrary to the south where the peasantry who made up most of the population clung doggedly to Christianity, they converted to the new faith wholesale. The stories of the great conquests of Muhammed and his successors in particular appealed to the Norse, and by the 10th and 11th centuries Islam was now being spread from the north as well; population pressures in Scandinavia drove them south and west in search of new lands. Heavily targeted were the British Isles, with Ireland being almost entirely overrun.
This however, would result in a reaction from the Christians. Ireland had been Christianized early and Ingland, while it had less of a Christian tradition, still strongly felt itself to be a lone outpost of Christendom in an ever more unfriendly world. In the 12th century, the Kings of the surviving Christian states of the British Isles banded together to form the Christianae Pacta — Christian Compact — an alliance against the "Infidels". Inglish troops in Ireland helped to beat back the Norse under the auspices of the pact, and at the Battle of Ferns soundly defeated them. That battle achieved almost a mythological quality, considered by the Inglish and Irish to have been the "Day that saved Christendom".
In the 13th century, the wealth and influence of the Muslim powers in Europe arguably reached it's zenith. Europe was dominated by three rival Caliphates; the Caliphate of Rum under the Perso-Turkic Begid Dynasty, stretching from the Alps to the Arabian Sea, the Caliphate of Francia under the Arab Hassanid Dynasty encompassing all of Western Europe, and the Caliphate of Maghreb under the Arab-Berber Zayanid Dynasty stretching from Hispania to Egypt. On the periphery, Scandinava had united into a handful of Emirates and a centralized Wendish Sultanate had arisen. Despite the strength of the Muslim powers, the Christianae Pacta remained undefeated, having established an uneasy truce with the Norse-Gaelic Muslim rulers of the Emirates of Alba and Ailech and the Southern Isles. Distrustful of the Pope in Rome, the the four Kings of the Pact elect their own Anti-Pope, who sits in Coventry and also serves as the closest thing the confederation has to a single secular authority; an inexorable relationship has developed between being Inglish or Irish and being Christian.
On the other hand, in some cities in Munster and Leinster the Kings of those states tolerate the populations of Norse Muslim traders there, as long as they remain inconspicuous. They also rely on the expert shipbuilding skills of the Norsemen; desperate to find another outpost of Christendom in the world and intrigued by the legends of Irish monks living on a great island across the sea and by the story of "Prester John", the Kings are increasingly occupied with the financing of new developments in the construction of ships and of great voyages, hoping to find the Lost Christians they believe reside across the horizon to the west...
Despite this, the Inglish fear the Norse more than all but the Devil himself — much more than they fear even the Caliphs or the "Cloaked Mohammedan" residing in Rome — the Norse took the romanticized tales of Arab military triumphs to heart and are fierce and unforgiving warriors and relentless sailors, and much to the consternation of the Caliphs have less compunction about respecting other "People of the Book" and less regard for the laws of war followed by the Arabs, and their theological deviations, particular their insistence that beer is a drink never forbidden by the Prophet and one which believers are free to imbibe as they wish; many a port town in Al-Firanja knows — and fears — the wrath of a drunken Norse trader.
With no Normans as such, there was no Norman invasion of Britain, and so the English language — "Ingelsk" as it it known to it's speakers ITTL — is much more Germanic in character; as evidenced by my use of West Frisian as a stand-in for it here.
* - The POD; IOTL he died fighting the Byzantines.