Yes you can do it now on the lawn. I used to maintain the bowling greens at Fairhaven, Lytham St Anne's. We always did the Scarifying in October. I don't see why not on your garden lawns.
Take a line from the bristol channel to the wash if below it and decent weather is forecast for about 5 days you have a little time if above it leave it til spring
absolutely no probs doing it now as long as it's not too wet or expecting frosts for a few days. We done our bowling greens at work this week but we are in Brighton where it's a bit milder.