Thanks for the replies Gents.
Yes we did start the watch when the Lufty 744 started his roll, not at rotatiion. Yes, it did take as long to clear the runway as to have waited and gone, but 40 tonnes of Fkker rotating where 400T on 744 had gone didn't seem a good idea.
Although we don't do FRA regularly, as opposed to other German airports, they seem to have given me more surprises than most. The best was changing ILS from 25L to 26L and insisting it was our equipment that had failed as they had a signal good indication in the tower. Further digging on the ground revealed a technician had changed them over without authorisation. Never mind, keeps you on your toes. Good job there's not too many new carriers with low experience levels.