Selling an Endowment

Charlie1

I have an endowment policy which matures in just under five years.
It's projected to pay out at 4% £27.600 at 5% £29.000 at 6% £30.500

I have enquired about selling and have had an offer of £22.900.

This endowment costs me £52 per month. I have a mortgage for £58.000. Would I benefit financially by paying off a lump sum on my mortagage?

Any advice would be most appreciated

Thanks
Charlie1