I have built this oven over the last year starting in February. I have tried to keep the cost down and think i have spent roughly £400.
The concrete blocks and storage heater blocks were free and the kiln bricks were second hand from a reclamation yard.
one thing i would say is make sure you have plenty of sand and cement! you may notice the concrete layer is a little thin, as i did this on a sunday evening and finished well after the shops were shut It does sit on a cross wall though that cant be seen in the pictures.
The cooking area is 36" x 28" and it heats to 250C in about an hour.
Still trying to find some decent wood to burn so i dont upset the neighbours too much!!