as someone new to this, I'm slowly developing an understanding of these issues. I got involved in the recent forum topic about PeteG's project for the 'new' 'old' Stonehenge.
http://www.themodernantiquarian.com/forum/?thread=34550&offset=25
Seems I may have put some people off with my smart-arse comment about Disco-henge. However, it was meant as a kinda warning about what has been done over here in the name of restoration/conservation/archaeology. (I know Pete's project doesn't intend to restore anything and is a completely new site.) The Newgrange 'restoration' is an interpretation of what they surmised from the limited evidence found. Ditto Knowth, a site I'm only getting to study now. I have very vague memories of a visit to Newgrange when I was a child. It was an overgrown mound in the middle of a field with easy access. Now – Discogrange, with visits mediated by guides.
The word that stands out in your quote above Littlestone is probably, i.e. "probably buried very close to where they once stood". On a probability, would it be right to restore the buried stones given that, to quote you again "It's now generally agreed by most restorers/conservators that if one is not sure what has been lost one leaves the missing area(s) blank"?
I'm not meaning to be trenchant here. As I said above, I'm learning and developing my own ideas and understanding. My own 'local' tomb, Seefin passage tomb,
http://www.themodernantiquarian.com/site/1253
could do with a bit of restoration. I'd like to see the chamber cleared and roof repaired. It wouldn't be able to be 100% accurate, but would maybe improve our understanding of the place and conserve this monument by protecting it from the elements. However, I'm ambivalent about this, given what may result from officialdom's surmisings. In the end, is it better sometimes to let bygones be bygones?
Andy