There should be a foam gasket under the fixing stud, and under the two clips - all gaskets get stuck onto the light cluster. My problem was, VW dealer, at MOT time, replaced a bulb and lost the gasket under the stud, so, a few years later, when I went to check the condition of the amber indicator bulb, the plastic wing nut would not come off - eventually I ripped the stud out then get the plastic wing nut off, cleaned up the stud thread (rusted up) and glued it back into the light cluster.
I think that there is a rear cluster gasket kit available from VW but what that includes I don't know - someone must have ripped the two clips out then!
There should be lots of guides to sort out that hose etc on
http://www.seatcupra.net (Ibiza 4) and
http://www.briskoda.net (Fabia) as they are all the same platform. Maybe join both these forums as well as the one your are currently on as there are lots more fixer-owners on these two forums.
One other thing to look for, when the rear wiper is sweeping, check that the washer spray nozzle is stationary and pointing upwards - if it rotates, that can be fixed with a repair kit from VW.