Well all good news. The dome works an absolute treat and because it was 900mm internal diameter I have inserted a 2 firebrick ring on the inside to generate a heat sync. Even though the dome was vermicrete it ended up very heavy so too 4 adults and engine crane to manoeuvre into place. Pizzas fantastic and cooking in about 90 sec. Internal temperatures up to 420c so far. Self made insulated door maintains heat very well but yet to cook breads or slow cooked meats as yet. Thanks for the advice.
Will post some photos when I can get uploading to work!