You'll be fine coming back into the UK.
There is no requirement to have 6 months left on your passport anyway, but as you live in the UK, you don't need to worry about passport validity. The only thing that matters is that your passport and visa are still valid when you return to the UK.
The main concern some countries have about making sure there are 6 months left is so that your passport doesn't expire while you are visiting another country on a short-term visitor visa... but the UK's policy is that it just has to be valid for the length of your visit to the UK. However, as you live here, you can just apply for a passport renewal from inside the UK anyway, so it doesn't affect you.