Hi Fella
3CC's spreadsheet is excellent but I think the calculations are based off an exit tax of 36% (it's now 41%) and a marginal income tax rate of 52% (on the basis of what you have written elsewhere, I suspect you have a significantly lower marginal income tax rate). If you adjust these rates (but otherwise make the same assumptions), you will arrive at a materially different result over a 16-year holding period.
My preference for equity investment outside a pension wrapper is a widely diversified investment trust (or, ideally, a dozen or so different ITs). That seems to me to be the best compromise between achieving a significant degree of diversification at a reasonable cost and (relative) tax efficiency.
I agree that investing in a concentrated portfolio of 10-20 individual stocks makes no sense unless you are prepared to put in a very significant amount of research to arrive at a conviction that your portfolio will beat (or even match) the return of the wider market - and even then you have to accept that you could be wrong.
Incidentally, if I was in your position I would still prioritise paying off your mortgage, notwithstanding the fact that you are on a cheap tracker, before investing anything in equities outside a tax-deferred pension wrapper. Totally risk-free return with zero tax complications or investment costs.
Edit: apologies, I've re-read your post and I see that you have re-run the calculations to allow for the change to the exit tax rate. Did you adjust the "dividend tax" rate for your own circumstances?