In the UK, pension contributions are paid into a pension pot that can not be accessed until age 55 (I think it's 55 but you can check this online quite easily) The 7% you mention will be the companies side of the deal. You would be expected to add a minimum (in our company 3%) but there is actually no limit on the amount you could put in. Although there is a point (around 40k) where tax starts to apply.
The key to a decent pension is to load up early in your career as the compound effects are huge. Most people don't and can't understand why they're going to live in poverty past 60.
if you can manage 25% including company contribution from your 20s you can conceivable retire on full pay!!