Immense, seemingly ignored round barrow upon Sugar Hill, Wiltshire:
http://www.themodernantiquarian.com/site/18158/sugar_hill.html

Superbly placed cairn upon The Black Mountains at Blaneau-draw:
http://www.themodernantiquarian.com/site/18177/blaneaudraw.html

The Brown Willy cairns, Bodmin Moor:
http://www.themodernantiquarian.com/site/3917/brown_willy_cairns.html

Excellent Mesolithic vibe at Great Upon Little Rock Shelters, West Sussex right at the start of last year:
http://www.themodernantiquarian.com/site/18105/great_upon_little_rock_shelters.html

Cerrig Blaencletwr-Fawr, northern foothills of my beloved Pumlumon:
http://www.themodernantiquarian.com/site/18447/cerrig_blaencletwrfawr_esgair_foelddu.html

Exceptional upland cist upon Buttern Hill, Bodmin:
http://www.themodernantiquarian.com/site/10341/buttern_hill.html
.....although the Trewortha cairn ran it close: http://www.themodernantiquarian.com/site/11123/trewortha_cairn_and_cist.html

And finally, for my money, the most perfect, inspirational little hill fort - Bryn Castell, Rhinogydd; to prove the point, prompting a visit up Diffwys later that week:
http://www.themodernantiquarian.com/site/18189/bryn_castell.html