Good story - have you looked into selling put options?
I am similar to you in terms of my portfolio - big secure cash-rich dividend-paying companies. I stay 80+% in stocks all the time, with a little in cash, but I use the full 100% as collateral to sell put options on those same types of company - just US ones for liquidity - Nike, Kimberley Clark etc
With a portfolio your size, I would be looking to achieve your annual £12k target every two months.
I wrote a few posts about it when I first started on steemit a few months back
Something to think about
Cheers