I'm sorry you are wrong on both counts. Northumbrian is a different dialect to Geordie as you have said. The other dialects from the area are Makem and Pitmatic. Northumbrian being the accent that is common in the larger part of 'Northumberland'. I being from Northumberland myself actually know what I am talking about. If you live in rural Northumberland, bearing in mind that the shire (as Northumberland is a shire county) is mostly rural, you would have a different dialect to someone from Newcastle, Prudhoe, or Gateshead, as the inhabitants of these places generally speak with a Geordie accent. Also no serious linguist would call all these *different* dialects Geordie. I have heard them grouped as Northumbrian dialects but not Geordie dialects. Calling them Northumbrian is correct for two reasons, one being that all these dialects come from the area that is known as Northumbria (That is Northumberland, Durham, Newcastle...etc..).

On the other point you are mistake. England (though not the whole UK) can be (rightly) called a Germanic nation. It is true blood is not the deciding factor as you say (though it is connected in some ways), however traditions, language, laws and history are! England was of course founded by...you guessed it Germanic tribes (whether they are the predominant DNA is besides the point. These tribes were the Angles, Saxons, Jutes and Frisians. You can't deny this as before the English kingdoms, England did not exist. Our language is obviously Germanic (though it has borrowed from other languages over the centuries, it is still West Germanic). Most of our common traditions, such as Yule (Yule itself is a Germanic Word, derived from the Norse Jul) are Germanic, the eating of a Christmas Ham, Mistletoe, Christmas trees, Yule Logs...etc…are all Germanic. Many of our laws come direct from Anglo-Saxon and Danish laws, though I agree many were modified by the Normans, who though descended from Norwegians are not culturally Germanic.
As for self-identity, I would say that the English identify themselves with Germanic culture, albeit in a subliminal way, for example the fact that they use Anglo-Saxon to describe themselves is an indication of this. They are identifying with tribes that were Danish and Northern German and thus Germanic so on that score yes the English are a Germanic people.

And as you bring up DNA casually, then firstly I will point out that it isn't proven either way whether the Anglo-Saxon DNA is more prominent or whether the British (used in this sense as pre-Anglo-Saxon) is. Different surveys have different results, and none have actually been accepted by all experts. And for the most part many of the newer surveys still show that in the North East of England the Germanic percentage is higher than the British (thus the predominant DNA is Germanic), the main problem is that it cannot be determined whether it is Anglo-Saxon or Danish "Viking" blood, but this does not make any difference to whether the blood is Germanic. I don't care whether the Modern English have British or Anglo-Saxon blood as I am partly Norse-Gaelic and partly 'English'...thus being a mix. I just do think that the Anglo-Saxon blood is prominent as do many experts, in North Eastern England.

Either way Germanic Blood or British Blood...the English are ethnically Germanic.

Note: I am not going to lie and say I am not proud of Germanic Culture as it is obvious (especially by my username), but I do consider myself British as the UK isn't about one ethnicity or culture but about the union of many and I am proud of that also. And by the way there is a good case for Northumbria being one of the more Germanic parts, due in a large part to it's folklore especially it's creatures, that include Dvergar (Which they are actually called...they are Dwarves) and Álfar or more correctly Ælfe (as they are in Old English), who are known by the common English word Elf, but are the older and if I may say more correct type.