Yes, Stonehenge and Avebury is a big topic for a 10,000 word dissertation.
There is a great deal of history to the current Stonehenge scheme. But it
all depends on the focus of your dissertation as to whether it's too much
for the amount of words.
Regarding your PS - it depends on what your audacious analogy is - does it
help to elucidate the conclusions you've drawn? You're probably going to
need all the space for a well-argued conclusion based on the material
discussed in previous chapters.
I hope that's gentle enough for your frayed nerves.
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