First, you need a font that has the euro symbol.

Windows:
Launch Character Map (Start > Programs > Accessories > System Tools > Character Map)
Select the font you want.
In the "Search for:" box, type "euro".  Should find the euro character for you in that font.
Double-click to move it into the "Characters to copy" box.
Repeat for any other symbols, like "pound".
When you have all the characters you need, click the "Copy" button to copy to the clipboard.

Switch to Photoshop, select text tool.
Paste.

You will need to use the Text tool in Photoshop.
As mentioned above, the font you use must have the euro and pound symbols in the character set.

Once you've found a font with the symbols use the following key strokes:
Hold down the ALT key and press the keys on the NUMBER PAD not the numbers above the letters on your keyboard. Once you release the alt key, the symbol will appear.

You can use ALT+0128 for the € symbol.
You can use ALT+0163 for the £ symbol.

Or copy the symbols from the characters above and paste it into Photoshop.

Providing both ALT-0xxx codes _did_ satisfy the exact requirements of the question.  But it ignores the larger problem:

1. ALT codes are an obscure (and outdated) method for calling characters
2. ALT codes only address a small portion of the characters available in modern fonts
3. OP doesn't know where to find obscure ALT codes
4. Microsoft provides a tool for finding the code, or more practically, to search visually and by name for the character
5. for keyboards with an embedded 10-key, it's impractical to use ALT codes
6. ALT codes require memorization of a few symbols, or a reference chart (or constantly coming to EE for help!)
7. "I know it when I see it"...visual recognition is far better than rote memory.
8. ALT codes do not address non-alphabetic fonts, like dingbats or other symbol fonts.

Try using character map and type "cedilla" in the search box.  Only 3 of the 29 characters with a cedilla are available with ALT codes.

Try "ligature".  None of those have ALT codes, but are used often when setting type.
cedilla.jpg