Should i pre warn my LL about handing in my notice

System

I'm in a similar position right now. I was meant to have completed on my purchase 2 weeks ago, and it's not looking like I'll complete for another 2 weeks. If I had given any kind of indication to the letting agent or land lord, I would probably be homeless by now.

My landlord as proved to be very twitchy in the past. I was previously renting with someone else and they moved out. I told the landlord and said I was going to stay and pay the full rent, they promptly served me 1 months notice. Luckily at the time, I was able to find someone else to share with and we signed a new 6 month agreement. I learnt a valuable lesson that day, don't tell your landlord anything until you're 99.9% sure you're leaving.

As it stands, I've missed the chance to give 1 month notice in November, so I'll be "stuck" with this place until near the end of January now. I won't be giving notice until I have to, which will be 3-4 days before the date stated in the contract.