Thanks Steve - Aqua Mix Heavy Duty Tile & Grout Cleaner Degreaser mixed at the recommended ratio, pre-wet, plenty of dwell and honing powder. This method worked fantastic as it always has in the past apart for just this small area of a few inch that looked ingrained in the grout and more black in colour rather than a dirty colour and with the pooling of the seal in the same area I'm guessing it may be oil/Greece based as it is near the oven as well, only thinking out loud though!. I even tried a few other alkaline cleaning solutions almost neat and scrubbed it by hand which improved it a little more. Like I said she was really happy with it, maybe I'm being to fussy but I'm a perfectionist and would be interested to know what others who have more experience thought.