I am a Brit who trained in NZ, worked in SA and who now is in specialist training in Aus. Unfortunately I have never worked in medicine in the UK, and so have no first hand experience of the current UK speciality training program and the status anxiety which it seems to generate.
Ultimately the only person who can decide whether the time and situation is 'right' is yourself.
Some advice given to me a while back by one of my mentors was to train in the place where you want to stay. It is becoming more and more difficult to transfer specialist qualifications between countries. In my case, I have had to prove to the GMC that I can speak my own language to work in my own country ( I had to suffer the indignity of sitting the IELTS...before the PLAB...as I trained in NZ).
There is a fair amount of popular rhetoric about work in NZ, Aus and SA. Having worked in all of them, here is my two pence worth :
SA. Rural medicine generally under resourced, often under supervised and can be over exposed. HIV and trauma are serious issues. Metropolitan life is hazardous - there are some dangerous places in SA !!! Registration is a bureaucratic nightmare....get someone to help you through the process and start about 6 months before you plan to go there. There is also immigration paperwork which itself takes time and energy to complete.
But...it's a fascinating and vibrant country, easy to get to from UK, some great people and there is some great healthcare (albeit mostly in the private sector now). Some of the best tutors I have had the pleasure of working for have been South Africans. Unfortunately they have their own exodus at the moment and many are headed to Aus. Money - very hard to make ends meet on a state salary, most MOs will supplement their income with private/locum work. This would probably be out of the question for a non South African.
NZ. Trained there and did my internship there. Many Brits like the fresh air and countryside, but few stay for more than a couple of years. The country is quite isolated from the rest of the world. Medical system is having serious problems with staff shortages (hence easy to get work). This is generally due to most NZ grads jumping the ditch to Aus. Expect to work long hours for no overtime (one of the unfortunate scams which leaves NZ doctors disgruntled).
Aus. Curently work in Aus, and I like the place. Registration is difficult though not impossible to negotiate - coming from the UK expect to be 'tied' to a hospital for the first year. This also precludes any locum work. Lifestyle is good. Medicine is becoming more defensive and emergency med is veering towards over investigation and medico legal protection. Plenty of jobs around. Standard terms are 39 hour weeks plus overtime (I currently work around 60 hour weeks, though this is compensated for by overtime payments). Outsiders won't be considered ahead of permanent residents or citizens for training posts. Locum work very lucrative - easy to find ED work at $130-$150 per hour.
Hope this helps. As I said, it's where you want to be that's important.