Trimming hedge back to wood

[Twilkes]

We have what we have been told is a green privet hedge out front, and it's getting a bit misshapen - bulges where there shouldn't be any, much like a middle aged man (or woman, for that matter).

We hand trim it with shears, don't really want to go down the power trimmer route, but if we cut it back too much in certain areas it will be back to the wood.

How long would it take to take for new growth to come through? Now seems to be the right time of year to do it, as the green parts are growing fairly swiftly.

Or would it even grow back? Parts of it we would want to cut back 6 inches or more, is that too much?

[Twilkes]

Thanks - it's our front hedge, so from our window we see the side that doesn't get so much sun (the side we're not that bothered about), and the opposite side is street-facing and gets most of the sun so presumably will grow back faster. It's the street side we're looking to cut back.

Will probably attack it in patches this summer to neaten it up but not end up with large areas of brown.

I'm pretty sure it's this:

https://www.best4hedging.co.uk/privet-hedge-plants...