I wouldn't worry too much. Basically from your diagnostics the front window demister will flash unless it has a bright light shining on the solar sensor on the top of the dash board, or you do the test in bright sunlight.
The fresh air/ recycle light relates to the system pressure switch. To prevent expensive damage to the system when the gas levels gets low the pressure switch cuts in which stops the air con working until the gas is refilled and the system is reset as the codes are stored in the memory.
I wouldn't recommend pressing the valve again as the gas can be dangerous, but just because you can hear some hissing out it does not mean its full. If your tyre has 10 psi in and you pressed the valve you would hear a hiss but it still needs more air, same principle.
Take it to a garage that can re gas the system and reset and it should be fine, as 400bhp said your looking about £45 for this, and its an easy enough job. Plus I cant imagine them being too busy with air con problems this time of year.