Rust streaks from behind roof gutter

I have a 97 (P-reg) Symphony (Boxer chassis).  There are rust streaks on the front (windscreen) pillars emanating from under the gutter.  I need to remove the gutters above the windscreen and sides to see what is going on - presumably corrosion of the top of the steel body where it is joined to the GRP (?) hi-top moulding.  Does anyone have similar experience of this issue and/or know how to remove the gutters without breaking them?  Many thanks.

Worth reading..

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I have a similar issue on the front nearside of my 1999 Duetto.
The link from Paulmold is very interesting, thank you.
I'll add that to my list of jobs......mostly rust related!

Jollywalker

As has been said, the link from Paulmold is relevant and interesting.
When I bought my Symbol in 2002, a van with the same type of construction, a GRP roof grafted onto a cropped off Van, when I bought it the salesman said to me that the van would last a long time but if ever the seal between the roof and the van failed then that would be the end of the van.
I remember because it seemed so extreme and I thought it was remarkably honest for a salesman (before I had signed too). I said couldn't I just reseal it and he said the water penetration would have caused irreparable damage.

It would seem they can be repaired these day from what other people are saying. good luck.

Thanks everyone.  Looks like I have a big job to occupy my idle hours...