Sustanon 250 is commonly used in the UK. I started on it, though I'm now on Nebido, which is a slow release type of T. I started on Sustanon 250 every 4 weeks, which is the general rule for patients at Charing Cross GIC (the largest GIC in the UK). I was then put onto it every 3 weeks as my levels after a few months were too low.
Others start Sustanon 250 at every 2 weeks and then decrease the frequency if necessary - this is commonly done by the main private practitioner for trans people in the UK. Of all the guys I know who are, or have been, on Sustanon, to the best of my knowledge I've never met anyone who takes it less frequently than every 4 weeks.
A lot of guys over here are switching to Nebido, the slow release form. I started it back in January, and after an initial loading period it's given every 10-14 weeks (depending on blood levels around the 12 week mark. I started on every 12 weeks, and have just been advised by the endo to take it down to every 13 weeks instead. I've no idea what it's called elsewhere in the world, but I'm definitely pleased with it so far.