It would probably look like Frisian, which now has a lot of influences from the Dutch language (if by German influences in your timeline, you mean Dutch because logically it's closer to England). If not then it would look like Frisian with influences from the native languages of the Celtic family.
Actually, there is practically nothing left of the original Celtic languages of Britain in modern-day English, and this is not due to the introduction of Norman, which was a romance language, but to the Anglo-Saxons who imposed their own language at the expanse of the natives. There is also some genetic evidence according to which the native males were wiped out by the Anglo-Saxons. Most English males are much closer to the Danes than to the men living in contemporary Wales. This is an indisputable fact (there are several Y-chromosome studies in full support of this assertion). However, the cause of this genetic link is unsure. Perhaps in prehistoric times the Celts entered the British Isles through a coastal route, while the English came from Denmark and Northern Germany, and were therefore closer to the Danes even prior to the invasion. Another reasonable hypothesis is genocide.
Be that as it may, I fully share your views on the evolution of the English language: it would certainly sound like Frisian. That would be a beautiful language, I believe. Did you know that the language of Tolkien's Rohirrim, Rohirric, is in fact a version of Anglo-Saxon? Edoras, Meduseldë, Eowyn, Eomer...Sounds good, don't you think? Looks good too, by the look of Eowyn!
Maybe the Dutch and the English would have a sense of common cultural identity...
If you need more information on this subject, I recommend you visit the site of the National Geographic. Search for the Genographic project, and haplogroups R1b and I.