Thank you for your swift & knowledgable reply - I an fairly new to clay so am having to learn at a fast rate !
Your answer made sense, No, I did not wipe tiles before glazing so that could be worth a try.
I also used a Botz white shiny glaze as a base as I'm a little nervous of mixing the Tin Glaze powder and you don't seem to be able to buy it ready mixed.
Burnishing at the leatherhard stage makes sense too, I used a 20 percent grogged terracotta.
I used Amaco underglazes & stains on top of base coat - alas I only applied 1 coat so they came out a tad pale.