My best guess would be Ogof Hesp Alyn but I don't recognise the shot.
The pros are : It looks like that, it's not a million miles for you to get there, you may be sat on banks of silt (correct for OHA), you might be sat on rock of that colour (Also correct for OHA), you are not wearing SRT (correct, to a point, for OHA)
The cons are : You aren't covered in nearly enough shite
But the "Pros" have the balance of probability .....
I don't do Photoshop (tried, failed), but as Mike says it will be flash and shadows etc.
Ian has it though, OHA just before you get to the canal climb (so before the mud and sh*t). The big boulder that doesn't look slippy until you stand on it and almost fall off it.
Turns out I don't have that many photos of North Wales caves!!