Not a question, just wanted to share a bit of maths!
My mortgage balance is £80k, fixed rate 6%, 9 years left to run. I can pay off 10% of the balance without penalty. If I do so (£8k) but keep my monthly payments the same, my mortgage term reduces to 8 years and I save a whopping £6000 interest. Can't think of any investment right now that would guarantee a return of £6k on £8k over 8 years.
So if you're in a situation to make regular overpayments on your mortgage or pay a lump sum off the capital - definitely do the maths because the result may surprise you.