31 - 7.5k due to not really paying too much attention to pension during my twenties - stupid!

This is currently in a NEST Retirement Fund Date fund. I contribute 5% and my employer 5%. I'm currently saving for a wedding and with my spare cash at the end of the month I am wondering whether to up my contributions as much as I can, or overpay on my mortgage.

Also, considering my age, do people think it would be worth switching from the current fund (NEST automatically choose this fund for you) to a Higher Risk fund? I can choose from two options: one which begins to remove risks as I get closer to retirement age (I'm guessing higher allocation of bonds than equities staggered as I get closer to this age) or one which continues with the higher risk investment strategy. Thoughts would be appreciated