There are a few stones in Welsh churchyards, but many a dubiously prehistoric.

Here's a few:

http://www.themodernantiquarian.com/site/119/ysbyty_cynfyn.html

http://www.themodernantiquarian.com/site/6996/llangernyw_yew_and_standing_stones.html

http://www.themodernantiquarian.com/site/14257/st_cadfans_churchyard_tywyn.html

http://www.themodernantiquarian.com/site/135/four_stones_of_gwytherin.html

http://www.themodernantiquarian.com/site/7127/corwen_cross.html

http://www.themodernantiquarian.com/site/8407/maen_twrog.html