Hi
So basically I graduated in the summer of 2012 with a 1st class in Physics integrated masters (Masters + Bachelors but considered undergraduate degree).

I've applied for Graduate jobs in various sectors and a PhD in Computational modelling.

I got nowhere with the PhD application but with Graduate schemes/jobs I attended a few interviews and assesment centres (around 6). Unfortunately I've been rejected by all of them :)

So anyways I think maybe doing a Masters to narrow my interests may be a good thing ?

The two sectors that I find interesting and im thinking of are either:
1) MSc in Petroleum Engineering
2) MSc Business Analytics or Operational research or something related

So what do you guys think ? Is a Masters worth it or should I just brush up on my interview skills and application forms ?

I just fear my gap is getting too big.

If you've attended 6 interviews/assessments then your CV must be attracting people. Therefore, it might be a good idea to try and brush up on your interview skills before rushing in to a Masters. Unless you are totally convinced that another Masters will massively improve your job prospects, it might just end up being a complete waste of time and money.
Have you only applied for the one PhD so far? If a PhD is what you want to do, then I would apply for a few more. You don't have to have a Masters to do a PhD, especially as you have a first at undergrad.

Thanks for the advice :)
Yes I've only applied for one PhD, for which I haven't been formerly rejected yet but I applied 1 month ago, so go figure (I'm going to call them tomorrow to see whats going on).

A PhD would be ideal but only in a topic I really like e.g. petroleum/computational modelling. That's why I thought doing a masters in the exact same field may help ?! Personally I think Physics is enough, but its not up to me :)