Hi Rachel,
Geoff and Andy's answers are good for a repair but you will always have a problem with flash band as it is only good for a quick repair, ideally you should have Lead chased into the brickwork and onto the conservatory this way it will eliminate any more problems as there should be lead there from the start, its just the conservatory fitters using flash band to make there job easier and cheaper for themselves.
Hope this helps!
Regards Keith.
www.roofco.co.cc, August 2009