Very sorry to hear about this. It's a difficult situation for all
concerned.

You don't say how much help the British Embassy offered, but I suspect
they can only offer advice and contacts etc. As far as I know they do not
normally offer financial support.

From what you say the first priority appears to be medical, especially in
terms of getting your brother into a stable condition.
Until this happens your options are very limited and not without risk.

As far as I know the Air Ambulance Network offer what they call a
Commercial Medical Escort Service. They provide this specialist service
from bed-to-bed on commercially available flights, but only if the patient
is able to be seated and is medically stable. This would work out at reasonable cost
compared to dedicated Air Ambulance.

There is an organisation called - Foreign Assistance Center Philippines.
I do not know just how helpful they would be (I have never contacted them) but they
may well be able to help in keeping medical costs down where possible.
Again, I focus on this as it appears to be the priority.

I'm sure you already know just how expensive medical care can be in the Philippines.
You need to be aware that this care will likely cease when the funds are gone.
The reason I mention this is that you need to set up a secure route for any transfer of
funds from UK to Philippines.

Sorry not be of more specific help at this time, I will do some searching
and talk with some of my contacts in the Phils.
If I can help further I will respond to you.

Concerning the immigration status of the family to UK only the British Embassy can
advise you. Do not expect that any actions outside of current regulations would be
considered. From my own personal experience this does not happen.