Being an owner of a BGT, I only have Imperial taps and dies.
But if this is likely to be an odd job (and it's often worth cleaning out threaded holes prior to assembly with a tap - paint etc) you might find it worthwhile getting it from the likes of Halfords or MachineMart.
Otherwise, stick the frame in the back of your car and visit your local engineering business, they'd do it, and probably for a couple of beer tokens in the pocket.
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