Hi there,
Mystic makes a very good point about the execution only option. You can also do it this way through Cornmarket in which case they cannot charge the €300 fee. They may be reluctant to do this as they will feel they have given you the advice already.
As for Zurich, they are a very reputable pension and investment company. They were previously Eagle Star which you may be familiar with.
The policy you have mentioned would be designed as a medium to long term savings plan (Ie 5 years plus). It doesn't mean you cannot get access to your money but there may be exit penalties for the first 5 years, this should have been disclosed to you by Cornmarket.
You can also get access to the fund information if you visit zurichlife.ie
I would not have any concerns over dealing with Cornmarket as long as you understand the product. Check out the capital guarantee aspect, this may only apply on a certain date for example the 5th anniversary, so it is important to know how it works.
Also check what allocation rate you are getting. Is 100% of your money being invested? If they are charging you for setting up the policy you would expect 100% to be invested.
Hope this helps in some way.