This is certainly not a lodger agreement because there is no sharing of accommodation (such as kitchen or bathroom) with you. Therefore, the tenancy will either be a contractual tenancy or normal AST.

When the house was originally built was the annex part of that building? Or, has the annex been added since original construction?

The actual definition of resident landlord (which would require a contractual tenancy) is copied below. If the annex has been built after original construction, it’s more akin to a semi detached property and so would be a normal AST. Have a read of below but we might perhaps discuss this on the telephone tomorrow.

(1)A tenancy in respect of which the following conditions are fulfilled—
(a)that the dwelling-house forms part only of a building and, except in a case where the dwelling-house also forms part of a flat, the building is not a purpose-built block of flats; and

(b)that, subject to Part III of this Schedule, the tenancy was granted by an individual who, at the time when the tenancy was granted, occupied as his only or principal home another dwelling-house which,—

(i)in the case mentioned in paragraph (a) above, also forms part of the flat; or

(ii)in any other case, also forms part of the building; and

(c)that, subject to Part III of this Schedule, at all times since the tenancy was granted the interest of the landlord under the tenancy has belonged to an individual who, at the time he owned that interest, occupied as his only or principal home another dwelling-house which,—

(i)in the case mentioned in paragraph (a) above, also formed part of the flat; or

(ii)in any other case, also formed part of the building; and

(d)that the tenancy is not one which is excluded from this sub-paragraph by sub-paragraph (3) below.

(2)If a tenancy was granted by two or more persons jointly, the reference in sub-paragraph (1)(b) above to an individual is a reference to any one of those persons and if the interest of the landlord is for the time being held by two or more persons jointly, the reference in sub-paragraph (1)(c) above to an individual is a reference to any one of those persons.

(3)A tenancy (in this sub-paragraph referred to as “the new tenancy”) is excluded from sub-paragraph (1) above if—

(a)it is granted to a person (alone, or jointly with others) who, immediately before it was granted, was a tenant under an assured tenancy (in this sub-paragraph referred to as “the former tenancy”) of the same dwelling-house or of another dwelling-house which forms part of the building in question; and

(b)the landlord under the new tenancy and under the former tenancy is the same person or, if either of those tenancies is or was granted by two or more persons jointly, the same person is the landlord or one of the landlords under each tenancy.