An AVC is a great way of bolstering your income in retirement, if you can afford the extra outgoings each month. You're allowed to contribute up to 15% of your gross income, which could also include your flying play. I.e. take away what you currently pay into your pension from 15% (gross) of your salary, and you can contribute the outstanding percentage into your AVC. Contributing into the same scheme as your employer already uses will help to save you a lot of setting-up and running costs rather than going it alone with another provider.
Other things to consider should also include Individual Savings Accounts (ISA's) which have a tax free 'wrapper' around them.
Although I am a qualified financial consultant, I have not practiced for some years and only offer the above as a personal opinion! An IFA is the only consultation route to take.