I understand employment law changed last year to bring the rights of temp/contract staff in line with permanent staff. Can anyone provide me with a reference for further details or provide help with this scenario.

We have a number of direct temp staff who have enjoyed very similar benefits to our permanent staff. They receive contract rates, are PAYE and also qualify for holiday/sick allowance. Can we change their benefits by removing the holiday/sick entitlement that they have been used to receiving for approx 6 years? In other words, make their holiday/sick allowance inclusive of their rates of pay, without increasing this remuneration? Thank you in advance for support.
Craig Lewis