"The Tribunal, after taking into account the observations of the parties, may at any time determine whether its proceedings are to be treated, for purposes connected with ..." – I paraphrase here – any matter connected with those proceedings: "... as proceedings in England and Wales, in Scotland or in Northern Ireland and shall instruct the Registrar to notify the parties of its determination."
"In making a determination under sub-rule (1) the Tribunal may have regard to all matters which appear to it to be relevant and in particular the part of the United Kingdom where –(a) any individual party to the proceedings is habitually resident or has his head office or principal place of business; (b) the majority of the parties are habitually resident or have their head offices or principal places of business; (c) any agreement, decision or concerted practice to which the proceedings relate was made or implemented or intended to be implemented; (d) any conduct to which the proceedings relate took place."