[user104658]

It's supposed to be a seamless process but the honest answer is -- it isn't always, and people have been caught out. They'll backdate the money to the point of the application but it can take a fair bit longer than the time advertised to process the application... because it's a government function and thus full of inevitable inefficiency.

I don't mean to be a debbie downer but being brutally honest it doesn't really matter either way. Your "legacy" benefits end as soon as you apply, whether that's now or in a few months, it'll be the exact same process taking the exact same amount of time, unfortunately.

So the decision is fairly simple I guess.

If you have a good bit of money set aside now and you're worried about expenses later in the year (Christmas, winter bills, etc.) then apply now and get it out of the way ASAP.

If you'd be able to save up some extra as an "emergency pot" in the meantime and want that as a safety net, then wait as long as possible.

Otherwise like I said it makes no functional difference: As soon as they get your application your legacy benefits end, whether that's now or October, and your new ones backdate to the point of application. So you don't get more/less money either way, it's purely about considering when is most convenient. Or least inconvenient, I suppose... I don't imagine any of it is convenient.