Fire brigade will charge you.
Nope.
Ok, lets clear this up a bit from the 999 point of view.
There is no special service charge levied in relation to incidents involving the rescue of animals. Even rescues as innocuous as cats stuck up trees. If someone calls the RSPCA/SSPCA to report a cat stuck up a tree they will as already pointed out be asked how long the cat has been up there. If it is under or around 24 hours the caller will be asked to wait longer as the cat will in almost all cases, return to ground level at some point thereafter. Only if it is more than 24 hours (usually substantially more) will the RSPCA attend to size up the situation. In some cases they wont even attend but will call us. We will then attend and take a look. Most of the time we will remove the cat from the tree unless my DRA indicates that I may be putting my crew at risk in doing so. But usually I'll get the crew to rescue the cat, I'm not getting tipped out to a cat stuck up a tree only to arrive with an already 'tied up resource' only to say to the owner 'Nah, not really keen on that'. I'm there anyway so I may as well get on with it.
Now, sometimes an owner will bypass the RSPCA and call us directly. In which case I'll ask the same questions the RSPCA do including 'how long has it been up there?'. If its a short period of time I'll tell the owner to wait a bit longer but by all means if they feel the cat is in danger or in distress then give us a call back later if it still hasn't returned to ground level. Control room procedures/attendance procedures guide us here and we shouldn't really deviate away from them and just jump in the fire appliance and drive to the address concerned. However as a 'PR' exercise if someone does sound distressed on the phone that their little Tiddles is stuck fast then I'll nip out on the quiet in the appliance without making it a turnout via control. We'll then more often than not rescue the cat or simply give the owner reassurances that its not in any danger. People like being reassured and if that reassurance comes from a crew of firefighters who also say that they will in fact return at a later time if need be if the owner is still seriously concerned then they generally are quite receptive to that.
There have also been the odd occasions where one of my trainee development firefighters needs to tick a box on his portfolio involving animal rescues so we'll use any calls to a cat up a tree to do that too. Makes sense.
Finally, there are very few cat skeletons up trees nowadays which may tell you something.
If you are genuinely concerned for the cats welfare and ultimately, safety then by all means give your local fire station a call on their direct dial landline number, not 999. It does depend on who is on duty at the time as some folk will take a common sense approach in the same way I do but some others will play it completely by the book and refuse to attend.