On the passenger side of my Honda (left side,uk) there is allot of water coming in and making the floor very wet. I need to investigate further. I have checked sunroof drain and they are unblocked.
Can anyone give me some advice as where to start? Should I start with the inside of the car and remove some carpet and trim? Any help would be appreciated.

 

Remove seats so you can lay down, remove carpet so it doesn't absorbe the water, have someone with a hose start hosing down the windshield while you lay down there with a bright flashlight and locate the leak.

 

Check your heater core.

 

Would the UK civics have the same seam seal issue the USDM and CDM civics had?

 

At a certain age, I'd say yes.

 

Well, this TSB is for the USDM and CDM civics but it might also be something to investigate for you:

TSB_A92-050.pdf

 

Add the year MK5 to your first post.

 

On what side is you antenna located? if it is on the passenger side, check teh antenna area. Under the antenna base, and under the rubber molding that goes along the top towards the windshield.