The UK Unmarried Partner Visa (otherwise called the UK defacto visa) permits the unmarried accomplice to enter or stay in the UK on the premise that they are involved with an individual who is available and 'got comfortable in the UK'.
'Gotten comfortable in the UK' implies that you are commonly inhabitant in the UK with no migration limitations on the length of your visit.
The UK Unmarried Partner Visa applies to both hetero and same sex connections given that you can demonstrate that your relationship is remaining alive and has been in presence for at least two years.