I asked only a few days ago how soon is soon, to which no-one will actually answer. But the Stripe guy did say that he agreed that we shouldn't wait... go implement something else, and then they will help people move to them post-launch.
So don't not launch something in the UK because you're waiting for Stripe. Launch with GoCardless, launch with PayMill, hell... launch with PayPal if you have to.
Getting money through the door should be the only focus, not waiting for other people.
Once you've launched with another service, you may well be tied to them anyway, if they lock in your subscribers' card data. At best, you're running multiple services in parallel until all your early subscribers quit, or you're asking everyone to resubscribe and surely losing a significant number of people during that process.
And once you've launched with another service, you've permanently accepted their legal terms, which may or may not be a smart thing to do with some of the things these guys hide away in their contracts.
I certainly wouldn't wait for a company that says "soon" forever, but it's also not as simple as just signing up for any alternative you can find and hoping you'll move later. Of course you want to start bringing the money in, but as the saying goes, if you get into bed with the wrong partner for a night, the consequences can still last a lifetime.
Do you handle subscriptions and if so do you have any plans for handling moving the subscriptions from PayPal to Stripe?
If I were just to be handling one-off payments I'd not particularly care who I chose to go with (within reason). With subscriptions this gets, I believe, a bit trickier.