what job are you in? do you plan to stay in that job?
In my non professional opinion, occupational pension schemes provided by your employer are often the best value because they also contribute, rather than just you. However, if you plan to move around a lot in your job, or take time out to have kids, you could find yourself with loads of different pots of pension when you retire. An altternative would be a stake holder or personal pension which you can take to whateverjob you are in or can add to when you are not working. - just contact an independent pension advisor (yellow pages) or your work may provide advice.
Of course, there has been a lot of negative press about pensions recently and you might prefer to do something elses completely like get a buy to let place and sell it when you retire to release money