Apply to the Caudwell Trust for help with biomedical testing / supplements. The Caudwell Trust have been absolutely fantastic in supporting many families who have been unable to afford to fund biomedical interventions. You can download an application form online from http://www.caudwellchildren.com/
You can also apply for disability living allowance. http://www.direct.gov.uk/en/disabledpeople/financialsupport/dg_10011731
Those qualifying for the middle rate care component or higher rate DLA can also apply for carers allowance http://www.direct.gov.uk/en/CaringForSomeone/MoneyMatters/CarersAllowance/index.htm
If you qualify for middle rate or higher rate care component DLA you can also apply for increased child tax credits. For further benefits you can apply for http://www.direct.gov.uk/en/DisabledPeople/FinancialSupport/Introductiontofinancialsupport/DG_10020535