Hi Samri. If you are looking for FREE help, it is available. What you need to do is Google "Community Drug and Alcohol Team" for your area, ie "London". Get a number and call them. They will have your brother in for a meeting. This takes about 2 weeks for them to sort themselves out. They are the people who can also arrange funding so it is worth a go. I have to tell you it is a LONG process. As with all these sorts of things, they are inundated with people wanting help.
The other option is AA. Again Google AA for your area. They will have you in for meetings too.
I feel the cheapest help is to go for a Private Detox. These start at around £2,000. A detox should really be 2 weeks minimum. After that go to AA meetings to keep him clean.
As an example, If you and your brother, plus mum and dad, all put in £500 it might make it more affordable. Just a thought. Don't let it all be on your shoulders.
If you need any more help, post a message back on here. Good Luck.