Hello & welcome, I am Dr. B, a licensed veterinarian and I would like to help you with your wee one today.
Now since you mentioned that Chilli has bladder stones, I assume the estimate you have been given is for surgical removal of the bladder stones (cystotomy). If this is the case and you have been quoted £380, this is a good price (my own practice would charge ~£500 for the surgery) and one that you could certainly take advantage of.
In regards ***** ***** potential costs, it is worth checking to see if that quote covers any post operatve antibiotics or pain relief. Otherwise, that could potentially cost another £30-50. Finally, as I am sure you are already aware, Chilli will likely need to stay on a special diet to at least prevent crystal/stone recurrance even if it didn't dissolve her current stones. So, that would be another potential cost for her long term care.
I hope this information is helpful.
If you need any additional information, do not hesitate to ask!
All the best,