Make sure you read and heed the advice posted here. You really don't seem to be that sure of yourself, as you're even having trouble talking about this to your therapist, you have to find out WHY you want it. I don't even think it will not make you a better CD. Speak with your therapist about this and if the ok is given then they will usually give a referal for HRT to give to your GP. Research the WIKI here and get as much info on HRT as you can get and make sure you understand it, the risks, the possible side effects and results you can expect. My breasts show, and I mean really show so there is no way that I can dress in male cloths (not that I would now) as I would look a little odd.
HRT does not make a woman, it just helps. Your parents will notice changes, and they will find out. It's one of the steps you have to plan for, and you have to plan for the possibility that they may throw you out of the house. "Hoping" that you have a job if this happens, doesn't cut it. You should have one, for the security it provides, and it should be a job that can support you when you are on your own. You should also have plans for a place of your own before you start HRT as well. I'm not sure how available suitable rental accomodation is in the UK, but it's not that available here in Canada and I think it's the same in the US.
Don't be rash, as it could have tragic consequenes, and remember we're here to help you through this.