• 02.001 The washing-up was so dismally real
• 02.019 and quite unwashed-up,

The first is hyphenated in its sub-entry in OED.

The second… “washed-up” is a sub-entry under “washed”… and “un-” the prefix is a rabbit-hole which just stole from me an amazing half hour.  May I read you a bit?

1. Expressing negation. The prefix has been very extensively employed in English, as in the other Germanic languages, and is now the one which can be used with the greatest freedom in new formations.

  2. In Old English the number of recorded forms in un- is very large, the prefix being freely applied with a purely negative force to several parts of speech… Altogether the number of un- words recorded in Old English is about 1250, of which barely an eighth part survived beyond the Old English period.

 3. The disappearance of so many of the Old English formations left early Middle English with a very limited supply of un- words, even when new (or apparently new) examples are added to those inherited from the older language. A fair proportion even of this reduced stock proved unable to survive for more than half a century, and had passed out of use by 1250. A few of these, especially such as obviously had some general currency, are entered in their alphabetical places, but the greater number are given here (together with a few of somewhat later date) as properly belonging to the older period and having no direct influence upon the later development of the prefix. Most of these are composed of purely native elements…

I think it safe to say that while every part of “unwashed-up” is perfectly understandable, that this way of using these elements is originality on Tolkien’s part.”un-, prefix1.” OED Online, Oxford University Press, June 2017, http://www.oed.com/view/Entry/208915. Accessed 21 September 2017.

“washed, adj.” OED Online, Oxford University Press, June 2017, http://www.oed.com/view/Entry/225940. Accessed 21 September 2017.

“washing, n.” OED Online, Oxford University Press, June 2017, http://www.oed.com/view/Entry/225961. Accessed 21 September 2017.