You can ask for a pension 'quote' from the DHSS. They will tell you how much you have paid in and any shortfall. You can opt to take less pension or pay a lump sum upfront. I missed about three years of my pension payments and was told it would be around 6p per week difference so I opted to receive less pension and keep my capital.
I got credit for my years at university automatically in the 70s and for my year on a postgraduate course I took 30 years later (although I had to ask for the latter).
As sebhthion has said you can get a quote , although it's the DWP you want not the DHSS.