Compare Overpaying Your Mortgage Against Investing the Difference

Every month the same argument with yourself: overpay the mortgage or shove it in an ISA. One is a guaranteed return, the other is a bet on the market beating your interest rate. This lays the two paths side by side with real numbers, so you stop deciding based on whichever article you read last.

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You have {SPARE_AMOUNT} a month spare after bills. You are deciding between overpaying your mortgage and putting the money into a stocks and shares ISA. Your mortgage rate is [mortgage interest rate] and you have [years remaining] left on the term.
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<task>
**Compare** the two options on:
1. Likely financial outcome over 10 years under a conservative and an optimistic scenario
2. Risk profile of each choice
3. Flexibility: what happens if you need the money back early
4. Psychological factors: guaranteed return versus market uncertainty
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<output_format>
- Comparison table: mortgage overpayment vs investing
- Short verdict paragraph naming what would change the answer
- No generic disclaimers, just the trade-offs
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