I suspect that a witch seeking a witchy holiday wouldn't have much of a problem finding one in the history rich UK. I did a tour of Edinburgh a few years ago and the caves below the city are home to a witch coven and allegedly a great number of spirits. Then of course there are always the more traditional pagan sites like Stonehenge and the Avebury stone circles.
And Witches do have conventions, group gatherings with speakers of noteworthy status. As with any common interest there are opportunities to get together, swap ideas and meet a few friendly faces. But sorry, no one size fits all answer for a specific witch holiday destination.
Image http://www.sxc.hu/photo/1377467 (Mei Teng)