I'm British with dual Canadian citizenship. I arrived in the UK using my Canadian passport. When I went to Canada recently, I left my UK passport here (in the UK). When I arrived back in the UK the Border official said that if I'd had my UK passport with me he could let me stay in the UK indefinitely (stamp it). However since I arrived in the UK using my Canadian passport he could only validate my Canaidan passort - with 'conditions'. What I'd like to know is, can I have my British passport validated WHILE I AM HERE in order to stay and maybe work? Or do I need to leave the UK on my British passport and re-enter to validate my British passport?
You're British, so you have the right to live and work in the UK*. Entering the UK using a Canadian passport doesn't change that. There's no need to "validate" anything, so I'm not sure what the border officer would have been talking about. Any conditions on leave stamped in your Canadian passport don't apply to you.
*By "I'm British" I'm assuming you are a British Citizen, not one of the other kinds of British national.