Have a look on the Dti websitehttp://www.dti.gov.uk/index.html
Has lots of help for part timers, I believe you should be treated the same as full timers.
PART-TIME WORKERS (PREVENTION OF LESS FAVOURABLE TREATMENT) REGULATIONS 2000
FACT-SHEET FOR PART-TIMERS
The aim of the Regulations, which came into force on 1 July 2000, is to ensure that part-time workers are treated no less favourably in their employment conditions than comparable full-timers, unless this is justified on objective grounds. (The Part-time Workers (Prevention of Less Favourable Treatment) Regulations 2000 (Amendment) Regulations 2002 (SI 2002/2035) made two amendments to the Regulations, dealing with comparators and with access to pension schemes.)
This means that part-timers must receive (pro rata where appropriate) the same treatment as comparable full-timers. This will include no less favourable:
rates of pay (including overtime pay, once they have worked more than the normal full-time hours);
access to pension schemes and pension scheme benefits;
access to training and career development;
holiday entitlement;
entitlement to career break schemes, contractual sick pay, contractual maternity and parental pay; and
treatment in the selection criteria for promotion and transfer, and for redundancy.
In order for a claim to be made, part-timers will need to identify a comparable full-timer who is receiving more favourable treatment. There are several tests to establish who is a comparable full-timer. The part-timer must:
work for the same employer as the full-timer, and
do the same or broadly similar work (taking into account experience and skills where relevant) as the full-timer.
Part-time workers who believe that they have been treated in a manner which infringes the Regulations have the right to receive a written statement of reasons for the treatment. The part-timer must submit a request in writing, and the employer must return the written statement within 21 days. Part-timers who still believe they are being treated less favourably, and who are not satisfied that this treatment is objectively justified, can make a complaint to an Employment Tribunal against their employer. The Tribunal may require the employer to pay the part-timers compensation if it finds in their favour.
There is also protection for workers who return part-time to a job they previously did full-time.