Hi GordonI would assume a 5% return on average from the invested portion of my capital
Are you assuming an annualised 5% return, net of all costs and taxes, on the equity portion of your portfolio only? Personally, I think that's rather optimistic.
Incidentally, and apologies in advance if this sounds overly pedantic, the average annual return is not the same thing as the annualised rate of return (aka the CAGR).
Simple example -
Portfolio A
Invest €100
Year 1 - 20% return
Year 2 - 0% return
Result - €120
Portfolio B
Invest €100
Year 1- 10% return
Year 2 - 10% return
Result - €121
Portfolio A and B had the same average annual returns but different annualised rates of return.
This example also explains why volatility harms portfolio returns.
I still think paying down a mortgage invariably has the higher expected return (particularly on a risk-adjusted basis) given our tax code.