Roof Leak Berlingo Desire

[redhat]

Hi all,
My 1.6hdi 16v ('57) Berlingo Desire has started to leak water (cupful? after light rain) by the seam by the drivers visor. Googling seems to point more to the bonding coming apart in the roof module (five glass windows) than a loose arial mount.
1. does anyone know where best to fix this (I live in Reading, Berks):
a. citroen dealer (mucho dinero)
b. independent garage (will they know what's what)
c. independent windscreen or glass roof repairer (not Autoglass etc)
d. myself (reasonable diy)
Leading straight on to how is it fixed:
a. take off roof module and reseal (but will it leak again...)
b. pump bath foam sealant into gutter or under seal or in roof!
c. get citroen to admit fault and fix (in my dreams)
d. sell during dry weather (joke)

This appears to be one of those design/materials faults that manifest just after warranty expires but is sufficiently dangerous to warrant a responsible attitude on the manufacturers part - if water pours down while driving the surprise could easily lead to an accident.
I have an extended warranty with a non Citroen company. After any advice from here I shall try them...
If any other Desire owners have/had this water leak I would be grateful to hear from them. Maybe if there are enough we could effect some response from Citroen.
Regards