Premium Service Centre and 2nd Discretionary Leave

[jamber]

I'd like some advice. My wife was awarded discetionary leave to remain in April 2012 and her first 3 year leave is coming to an end soon. Her first application took ages so using the same day decision at the Premium Service Centre is tempting. I think her application can be decided there but I'm not sure. The UKVI website says it needs to be covered by the "transitional arrangements" and is "covered by the immigration rules". I'm pretty sure it's covered by the transitional arrangements (it was awarded before July 2012) but am not sure about the immigration rules. Please can someone advise me on this:

I'm British. My wife is Sierra Leonean. She'd already been refused an asylum claim when we met in London. We found a place to rent together and applied to the then UK Borders Agency. Over a year later we got permission to marry which we did. Another year later she got the first Discretionary Leave. Since then she has a good job and we have a joint mortgage and both our names on the lease.

I would imagine that the second term of discretionary is automatically covered by the immigration rules but haven't seen any paragraphs on it. Please help.

Thank you.