Alan,
The Form FLR(M) is the form used for Further Leave to Remain by a "partner of a person present and settled in the UK"
The UKBA definition of Partner is:-
- the applicant's spouse
- the applicant's civil partner;
- the applicant's fiancé(e) or proposed civil partner
or
- a person who has been living together with the applicant in a relationship akin to a marriage or civil partnership for at least two years prior to the date of application
Hope that helps and removes any concerns