I know its up the M25 to junction 27, then turn off onto M11 at junction 6 heading London bound for one junction to Junction 5 then you go right and its just near there, its called the seedbed centre i think.......... cant be more specific than that as i couldnt even find Junction 5 when i went the other night! the first exit i came accross was 4? there are roadworks going on so maybe they closed the exit or something? Not sure if its open on Saturdays either, might be best to call them for directions......