I doubt if they will be sufficiently strong to make the journey.
Having said that, in 1976, I saw a pair of house martins flying around the sea front in Westcliff on 20th November. Competely exceptional as I have never seen house martins or swallows after about the 3rd week in October.
Last year a mallard clutch hatched at our local park in mid-October. I doubt if any of them survived.
Southend RSPB have a page showing the first and last recorded sightings each year. Last year, someone saw a swallow on 29th Oct.