When to advertise rental

i wish to let my flat in London early next year. i assume tenants are not looking much now and perhaps i should AirBNB it for a shortwhile. im looking for 3 flat sharers for 3 bed flat. how long do such groups look ahead 2 months or much less. i assume most need to give at least 4 weeks notice but then some will have given notice.

Be mindful that a flat with three or more people in two or more households and sharing facilities such as a kitchen will almost certainly require an Additional HMO Licence, which can take quite a while to obtain. I think that this applies throughout London but check with your local council to make sure. If you do need a Licence, they will want to inspect the property and will require evidence that any works they want done have been done before they issue the Licence.
Also, if you’re a leaseholder and not a freeholder, the freeholder will almost certainly object to the flat being used as an Airbnb and it might invalidate your insurance as well. My freeholder made it absolutely clear that I couldn’t do Airbnb under any circumstances whatsoever.
I’d suggest advertising it about 4 or 5 weeks before it becomes available but you should only advertise it after you’ve got the Licence if you need one.
Hope this helps.

Thanks Robert thats a great help. i live in Hackney, London and when i last checked they had not renewed their normal selective licensing for under 5 occupant HMOs.

You would still need to follow the full HMO Management Regulations. There are also lots of other regs. Some with severe penalties for mistakes. Were you thinking of self managing? Do you have experience as a landlord?