am i entitled to holiday and pay rises

[pwak]

do charities have legal obligations to honour holidays and pay increases

[buildersmate]

Charities are an employer, the same as any other organisation taking on staff and they are bound by the same legislation.
Everyone is entitled to four weeks paid leave per year.
No employer is obliged to increase the pay of staff.

[aristotle]

DTI website tells you everything you need to know about employment rules and regulations www.dti.gov.uk.

[antiguru]

But note there has to be an employment relationship in place. That means you provide labour and they provide reward. If you volunteer an employment contract does not exist.