From CAB's www.adviceguide.org.uk:
Look at 'renting from a private landlord.'
The tenancy began before 15 January 1989
If your tenancy began before 15 January 1989 you could be either:-
a protected tenant (see below); or
an occupier with basic protection (see below).
Protected tenants
As a protected tenant you have the following rights:-
security of tenure. Your landlord can only repossess the accommodation in certain specified circumstances - see under heading The right to stay in the accommodation
the right to have the rent fixed by the rent officer - see below
the right to have rent increased only in certain circumstances - see under heading Fixing and increasing the rent
the right to have the accommodation kept in a reasonable state or repair - see under heading Repairs
the right of your spouse, civil partner, other partner or another family member to take over the tenancy on your death
the right not to be treated unfairly because of your disability, gender reassignment, pregnancy and maternity, race, religion or belief, sex or sexuality.
As Mummymeister says, whether you have a written contract or not, you are probably a protected tenant. I agree, go back and explain this - maybe it wasn't made clear before, but it should make a difference to the advice you're given.