At 0.9% over base gives a current payable rate of 1.4% .

You can get better rates than this by shopping around. Most 1 year fixed rate bond will give a better return if its just short term that you are looking for.

What you need to remember is that interest rates, although very low and are predicted to stay low for some years to come will not always be this low in the future.

It also depends how much you pay on a monthly basis and whether this is putting a strain on household finances. You could take a chunk off the mortgage and keep payments the same so your capital is repaid quicker shortening the term of the mortgage.

Hope this helps

Joff