I don't think Tolkien had a real-world template in mind when he came up with the Rohirrim. Or at least, not any one race or nation. In a letter he mentions 'Homeric horsemen', for example.
As for the Anglo-Saxon connection: it's true that he used elements of the language to relate the Rohirrim to the rest of Middle earth; A-S is to Rohirric as modern English is to the Westron. But that's about all. Let me quote from Lee and Solpova's excellent book, 'The Keys of Middle earth':
'(Tolkien) states that he was not trying to 're-create' anything but instead was at pains to note that: "No one would learn anything valid about the 'Anglo-Saxons' from any of my lore, not even that concerning the Rohirrim; I never intended that they should" (Tolkien: A30/1,f.121)'
(op.cit. pp.201-2)
The note in brackets refers to a shelf-mark at the Bodleian Library. Lee and Solopova are at pains to point out that others disagree with Tolkien; esp. Tom Shippey, who reckons the Rohirrim resemble Anglo-Saxons in every way, except their love of horses. But I agree with Tolkien - the so-called 'Anglo-Saxon' period covers many peoples and sub-cultures over time; from the migration days of the fifth and sixth centuries to the conversion to Christianity; from the time of Alfred up to the Conquest.
I think Tolkien was speaking professionally - he was not an A-S historian, and in these matters would defer to others who were; such as Sir Frank Stenton. I guess Tolkien was merely being precise.
BTW, Rumil - Tolkien did make a translation of Beowulf, but it hasn't been published - yet! I think you meant Tolkien wrote a famous lecture on Beowulf.