Lizardy

I applied for this visa from the UK 3yrs ago. Since then I've been travelling back and forth from the UK to be with my daughter and 2yr old grandson. I've been doing this on a visitor visa and leaving every 3 months. My current visa expires in April but I can't go back to the UK until Oct as 1) I let my house out. 2) I help with the care of my grandson whilst his parents work 3) I have met and fell in love whilst being here. My question is....can I apply for and extension of my tourist visa until Oct when we (new partner and I) fly back to the UK for a month and then return together? Would an extension stop me from reapplying for a return visa in Nov or even applying for a defacto visa if we decided to live together in the future. I'm so confused.