All opinion, not professional advice 
Have you investigated selling both with the commercial rental tenant in place? That might be seen as a bonus to buyers.
Realistically after costs do you think you're probably talking £115-120k as actual tied up cash.
So look at what your 120k is doing invested in property i.e. an 8k return but you're no doubt paying 20% agency fees/ insurance/ and need to allow a bit for maintenance so again trying to think of real in your pocket cash maybe £4,500/ year
So £4,500 (which is taxable) against a 120k investment is a bit under a 4% return (best check my maths though!) And theres also a time hassle factor. Also potentially empty periods in the future.
What mortgage rate are you paying, if its more than 4% and paying it off would give you relief then that would seam sensible.
If you're under 40 check out LISAs because whilst tied up long term when you do want to retire its very flexible tax free cash and topped up going in plus untaxed coming out where as pension contributions are tax free goung in but taxed coming out.
Standard stocks and shares ISAs are good, no tax to pay, and there are various funds you can invest in within them, so effectively you're paying a nominal fee for someone to invest in companies for you or you can start to put chunks of money across various companies yourself and create your own cross section stock portfolio.
If you look at sites like moneysavingexpert you can find accounts that are currently paying good interest.
Thinking about you current savings do you have a fairly accessible rainy day/ redundancy/ big bill fund? Something like three full months all bills and outgoings.
My opinion would be: if you're stable in your home and don't need to extend the mortgage etc in the future pay it off.
Put a chunk of money in a do not touch cash investment fund for emergencies.
Put a chunk in a LISA (if you're under 40)
Start your own stocks and shares ISA's for you and your DH.