It really depends what you are trying to get out of it, and you will need to be clear about this with any you contact.
Is your partner male / female?
Are you looking to both be submissive, or will one of you be the Mistress's "assistant"?
Are you looking for a bit of kinkiness, some serious pain, bondage / restraints, strapon etc?
Are you looking for a dungeon or domestic setting?
Would you be happy with a transsexual (pre-op or post-op)?
How far from Leeds?
Thoughts that come to mind are:
Mistress Vanessa in Batley - good dungeon and equipment
Mistress Violator - Bawtry - amazing looking post op domme with amazing dungeon
Mia in Leeds - BBW very experienced
Helena near Huddersfield
Mistress Raven - Sheffield
Lady Dark Angel - Sheffield
Lyla Rose - pre-op TS Sheffield
Mistress Linda - experienced older lady (Vanessa's mum)
Some kind be found on AdultWork, and a lot of them can be found on these sites:
External Link/Members OnlyExternal Link/Members OnlyExternal Link/Members OnlyExternal Link/Members Only