Audi A3 Fuel Tank Vent

Hi all,
I've seen some earlier threads talking about gurgling in the fuel tank and hissing from the filler cap and that sounds like the issue I'm
having with my A3 - 1.8 T Sport
When I open the filler cap a hissing sound is emitted and a strong whiff of petrol vapour and gurgling from the tank itself. If I don't open the cap every so often, petrol starts to leak out of the cap (not gushing out).
Anyway, if it is the Fuel Tank Vent, as talked about in other threads, please can someone tell me where I can find this on the A3?
There's a small indent in the seal around the filler cap which looks like it might be a vent of some sort, but it doesn't appear to be blocked (I gently pushed a cotton bud into it and it came out a bit gunky but didn't jam up).
Any thoughts? - the thought of petrol leaking out is a bit of a worry.
Thanks All
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