Perhaps I can offer you an answer, in place of the bickering.
You do have an employment contract - read this link.
http://www.direct.gov.uk/en/Employment/Employe es/EmploymentContractsAndConditions/DG_1003710 9
This is the best place I know of for impartial advice in this area - you should also be aware of the free advice line that ACAS run - far more useful than joining a Union.
As you will read, the main parts to your contract are:-
anything he HAS given you in writing
custom and practice (i.e. what's been going on around the patch recently)
anything like a general document issued to all staff - like a general notice or handbook perhaps (sounds like a faint hope from this idiot).
Your terms and conditions are a combination of all of these things.
What he appears to have ever failed to do is give you a 'written statement of employment particulars'. An employer must give this to each employee within 2 months of their start date and it must include the following as a minimum:
your pay and how it will be paid, your hours of work, your holiday entitlement, the sick pay arrangements, notice periods, and information about disciplinary and grievance procedures.
You could pull him up on this, if he's that useless, he probably will do nothing.
Under statutory regulations, you accrue one week of notice period for each complete year of service - so for you it is now 4 weeks notice - unless his terms indicate more than this.