We do not supply any flashing with our DIY conservatories as there are plenty of products on the market to do the job from lead to conservaflash. It is the customer's choice.
However in order to ensure that the conservatory is leak proof, it is essential that whatever flashing is used is fitted correctly. The main cause of leaks on conservatory roofs is that the flashing has not been let into the house wall sufficiently and / or that the overlap onto the roof is not sufficient. A little care at this stage of fitting will save hours of trouble later.