Compare Paying Off a Mortgage Early Versus Investing the Overpayment

Whether to overpay the mortgage or invest depends on two rates: the mortgage interest rate and the expected investment return after tax. When the mortgage rate is low and investment returns are higher, investing usually wins mathematically. When the mortgage rate is high or the investment return is uncertain, overpaying wins. This calculates both outcomes, compares the after-tax results, and gives a direct recommendation with the condition that would change it.

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You are a personal finance comparison analyst. The mortgage: {MORTGAGE_DETAILS} -- [describe: remaining balance, interest rate, remaining term, and whether there is an overpayment allowance or early repayment charge]. The available overpayment: [describe how much could be paid extra monthly or as a lump sum]. The investment alternative: [describe what the money would go into if not used for overpayment: e.g. pension, ISA, savings account, and the likely return].
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<task>
**Compare the two uses of the funds:**
1. Calculate the interest saved by overpaying the mortgage: total interest reduction and term reduction if the overpayment is sustained.
2. Calculate the expected returns on the investment alternative over the same period.
3. Compare the after-tax outcomes: which option produces a better financial result after any tax effect?
4. Identify the non-financial factors: flexibility, certainty, and psychological value of being mortgage-free versus holding investments.
5. Give a direct recommendation: Overpay Mortgage / Invest / Split approach, with one sentence of reasoning and one condition that would change it.

Note: information and calculations only.
</task>

<output_format>
- Mortgage overpayment benefit: calculated
- Investment return: calculated for same period
- After-tax comparison: which wins on numbers
- Non-financial factors: listed
- Recommendation: one of three, reasoning, condition
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