Reliability and Accuracy of familysearch.org in finding royal descent

I've been surfing around on familysearch.org today looking for leads on
some my ancestors, specifically Christopher Hussey who married Theodate
Bachiler/ Batchelder. I usually do my searching in person, but I have a
handful of lines that I can be pretty sure are credible thanks to
established records, DAR records, etc. This line is one of them. (In
fact, these people have so many descendants that I'm probably a cousin
to some posters here.)

Christopher Hussey goes back to his father, John, and Theodate goes back
to her father Stephen. Here's where things get hazy, though. I have
found a ton of websites, plus LDS site entries that follow the Husseys
back to about 1014. These seems relatively reasonable and one website
had transcriptions of the records that supposedly prove this line. I
think, based on the common last name, that the people probably are
related, and maybe even similar to the lineage I can find in websites.

These seem to be reasonable guesses, but things get even sketchier:

Supposedly, in the mid 1400's, a Sir William Hussey married an Elizabeth
Berkeley.
Following her line, I find all kinds of genealogies that claim she
descends from some sheriffs and minor nobles to the de Berkeleys as on
this webpage:
One of the de Berkeleys married the daughter of Richard Fitzroy, Baron
of Chilham who was an illegitimate son of John I 'Lackland', King of
England. From here, the line obviously goes to some major historical
figures such as Eleanor of Aquitaine, Charlemagne, Alfred the Great,
William the Conqueror.
From what I can find, these particular de Berkeleys and their relation
to the kingship are verified via "real" research and acknowledged
peerage. However, none of the verified royal lines that I can find go
far enough down the real de Berkeley lineage to verify (or void) my own
connection (especially since Elizabeth supposedly comes from a non
firstborn.)

I know that it is not impossible to find ancestors linking to this type
of royalty, especially since nobility is better documented. But... how
can a monetarily challenged grad student separate fact from fiction?

Tons of sites have this descendancy, and I don't know if it was somehow
verified, or if they are all passing on conjecture from a single source.
Is there a good way to find out which lines are verifiable and accepted
by genealogical societies, etc.? Surely, even an illegitimate king's son
has a traceable genealogy.
I'm trying to find reasonably verified (in lieu of a trip to England!)
sources to work up from the Husseys or down from the de Berkeleys.

Any ideas? Or can anyone offer if this is a known to be bogus genealogy
or not?

singhals...

Off the top of my head -- find the heritage group called something along
the lines of Illegitimate sons and daughters of the Kings of England ...
They positively glory in disproving illegitimacy.

As for the other question -- on the Familysearch.org site, if you're
looking at the Ancestral File portion, check the submitter; if it says
Medieval History Dept, that's as good as you'll ever get, right or
wrong. Otherwise, it is safest to assume that everyone is quoting
either one another or some common single source. WHAT that source
is/was may take some digging, during which you will want to keep
itemized records of who said which when.