Not sure what the complexity is then - you just need either a general FTSE short or individually short each share in your portfolio for a more exact match to the value of your holdings. The issue seems to be one of you calling market timing, and that is essentially what everyone on this website (and the investment world more generally) is trying to perfect! That sounds a bit fatuous, but there is no easy answer. Personally that's why I'd look at options. If it's a temporary correction it should all be over within a month or so, and if it's more serious than that then it should start to be more evident if things are still heading down in a months time. The key is that you will pay a known premium for a known amount of cover for a finite amount of time. They are complex, but worth reading up on if you want to hedge seriously.
My point about CFDs is simply that it's best to hedge on the same tax basis as your underlying positions. Unlike spreadbets CFDs are taxable. So if you placed your hedge and the market started rising, you could offset the losses from the hedge against the gains in the portfolio. It also means that if the hedge works, you'll pay tax on the gains, but that's offset by the fall in portfolio value. Using spreadbets you wouldn't be symmetrically hedged depending on whether the market went up or down because of the tax issue.
In terms of your questions like: "what point to activate the hedge, whether to phase the hedge in and at what point to set the stop loss level if at all? " those aren't hedging questions, they're market timing questions: you're simply asking how to trade around the market downturn, it's just that you're doing it from the position of neutralising existing exposure rather than opening new shorts. But your questions are exactly those anyone looking to short the current correction would be asking themselves.