I found the bullet points below on the ACAS website - I am assuming that you are working directly for the company (as opposed to say a freelancer ect) An employer cannot include an amount for holiday pay in the hourly rate (known as rolled-up holiday pay).
Key points At least the statutory holiday entitlement (5.6 weeks) must be given to workers -employers may give more under contractual term. Part time worker are entitled to the same amount of holiday (pro rota) as full time colleagues. Employers can set the times when workers can take their leave - for example a Christmas shut down. If employment ends workers have the right to be paid for any leave due but not taken. There is no legal right to paid public holidays.
So you and your employer could agree that you wont take holiday when your there but they would have to pay you half of the years worth of holiday (given that you would have worked 6 months) at the end of your contract.
Ive been offered a FTC may-oct. The hourly rate is very attractive. Can they include holiday pay in the advertised terms? What I mean is can they say I cant take any holidays during the employment but wont get extra pay for them either. Cant seem to pin it down on gov website