Held at The North Somerset Showground BS48 1NE on the first of the May Bank Holiday’s every year http://www.nsas.org.uk/north-somerset-show/blacksmiths/
You can download the official 2017 schedule at this link http://www.nsas.org.uk/wp-content/uploads/2013/03/schedule-17.pdf
Entry online is available at http://www.nsas.org.uk/north-somerset-show/blacksmiths/blacksmiths-entry-form/
Paper entry (to print off and send by post) is available at http://www.nsas.org.uk/wp-content/uploads/2013/03/IRON-WORKING-ENTRY-FORM-A4.docx
Some pictures of the Show at this link Somerset Show Photos.