What is the best way to fix a leak in a conservatory, London? ?

First fed up of the UK weather lately, London pours. And two, I have a problem surfacing through the polycarbonate roof. a lot of rain recently and it is leaking. What sealant can I try before I have to trudge down to Albion locally who I am wishing I should have used. Mine looks like this http://www.albionwindows.co.uk/products/conservatories-london.html but is not from albion. Probably should have gone with them now.