I wanna offer blowjob services, is Vivastreet a good place to advertise?

It's probably worth a try, but there are dedicated directories for male escorts that won't have quite such an onslaught of timewasters. You'll still get some though, just like anybody putting a new ad up .

Yes a lot likely do, but so does Vivastreet (or at least it did; it may not now). VS is also expensive and temperamental, although it might be more useful to you in London than it is for female sex workers.

If you want full control, you need a website.