The
statutory holiday entitlement of your full time colleagues (assuming that their 40 hours are spread over 5 days per week) is 24 days per year, including all dates upon which the company is closed for business (such as public holidays, if appropriate). This is calculated as 4.8 times the number of days they work each week.
Since every employee's contract with an employer is entirely separate to that of any other employee (unless there are agreements to the contrary), your employer is not obliged to work out your holidays pro rata to 25 days. You might only be entitled to the statutory minimum holiday which is 4.8 working weeks.
4.8 x 23.5 hours gives you a
statutory holiday entitlement of 112.8 hours.
Scaling it up in the same way that your full time colleagues have had their statutory entitlement increased gives you 117.5 hours (if they get 25 days including public holidays) or 155.1 hours (if they get a total of 33 days holiday, including public holidays).
This link confirms your statutory holiday entitlement. Anything else is determined by your contract:
http://www.direct.gov.uk/en/Employment/Employe es/WorkingHoursAndTimeOff/DG_10034642
Chris