How are holiday hours accrued, is it calculated by the month, week or hours. I don't know how to work it out.

You will accrue holidays in line with the published government guidelines which can be found here https://www.gov.uk/holiday-entitlement-rights/holiday-pay-the-basics

An associate will be entitled to a maximum of 28 days’ paid annual leave in each complete holiday year inclusive of bank holidays. Adecco's holiday year begins on the Monday immediately following the last Friday in September and ends on the last Friday in September. All paid annual leave must be taken during the leave year in which it was accrued and may not be carried over. Entitlement to paid annual leave accrues in proportion to the amount of time worked by the Employee. The Employee will be entitled to payment in lieu of any accrued but unused holiday entitlement upon termination of employment.

Payment for paid annual leave will be calculated by reference to the Employee’s average pay over the most recent 52 weeks (or the number of complete weeks the Employee has worked if 52 weeks of pay data is not available) to calculate the weekly pay rate. Paid annual leave must be taken at such times as are agreed by Adecco.

The Employee may under the Agency Workers Regulations 2010 become entitled to additional days of annual leave. Any such entitlement will be notified separately.

Full details can be found in your contract of employment.

Every week accrued half a day

Every week you work you very half a day of holiday. So after you worked two weeks you have a day off, after a month you have two

Holidays were accrued according to the length of service