Mortgage Repayment Dilemma

Titfield

I have three buy to let properties:
Property 1 Mortgage Outstanding £74K - interest only mortgage capital sum repayable in January 2024. Int £140 pcm
Property 2 Mortgage Outstanding £52K - repayment mortgage due to finish May 2027  Int £142 pcm plus capital repayment of £500 pcm
Property 3 Mortgage Outstanding £44K - repayment mortgage due to finish May 2028 Int £91 pcm plus capital repayment of £366 pcm
I have inherited C£100K in the form of stocks and shares.
What would be the most advantageous thing to do?
I am struggling to come up with the logic / formula how to work out the best answer.

getmore4less

What return are you getting off your investments?
What yields are you getting from your properties?
What rates are your debts?
What tax are you paying on your letting business?
What plans did you have for future financing?

Titfield

Return: I dont have a return yet on the stocks and shares as I have recently inherited them but would expect them to be inline with ftse.
Yields: Property 1 Gross Yield 4% on value 10% on original purchase price.
Property 2 Gross Yield 4% on value 10% on original purchase price.
Property 3 Gross Yield 3% on value 5% on original purchase price.
The mortgages are similar at 2.25 or 2.5% rate.
40% tax on letting business.
Only property 1 is interest only. I was going to remortgage or sell one of the properties.