It is a legal requirement that your employer provides you with a written statement of employment within 2 months of your starting work. It could be provided to you in several parts, one of which could be the Company Handbook. The basic minimums things that the employer must confirm in it are here
http://www.businesslink.gov.uk/bdotg/action/de tail?r.l1=1073858787&r.l3=1073971494&type=RESO URCES&itemId=1073791868&r.l2=1074428798&r.s=sc
One of the things you will see listed is your pay and how it is calculated. This at least would give you the very information on which to work out your holiday pay.
Chase your employer up - he is breaking the law.
However, when you do get it, I think you will find they will confirm that you get paid a basic week in holiday pay - and if that is 40 hours, then that's what you get.