dear Fine,
have you asked in the UK Support Forum? Local LowCarbing :: UK

Possibly some of your fellow UKers have done some of this hunting for you, if you still want what is also known as Vital Wheat or Vital Wheat Gluten or Vital Gluten or High Gluten flour. The trick is to check the ingredients or Nutrition info when you find a flour that might be the one you're looking for, and ENSURE it's 70-80% protein, then you've got the right one.

Good luck to you.