@bingowingsandthings if you start hanging out on pension forums, that’s often called “The Number” 
And it’s different for everyone.
- will you have your mortgage paid off?
- how much state pension will you have?
- how lavish a lifestyle do you want?
- are you on your own? (although you can’t guarantee anything with a partner)
It’s best to work out what you need first. Be realistic - if you know you can’t save much then 3 foreign holidays a year in retirement ain’t happening! Remember that your heating bill might be higher as you’ll be home more - but you won’t be buying new work clothes, or maybe spending out on commuting costs. Remember you’ll still be paying income tax even though it’s pension income, but after 67 no NI. You can take 25% of your pension tax free though - either in a lump sum, or 25% tax free on each withdrawal.
Say you work out that your mortgage will be paid off, and you want £16K a year gross. If you have (or are likely to have) a full state pension, you need an extra £7.5K a year.
You mention age 60 - you also need to factor in extra money to bridge until your state pension starts. For me, that’s 67.
A quick way to estimate it is to look at annuity rates. You used to have to buy an annuity. That’s where you use your pension savings to basically buy a promise to pay X amount until you die. It will be adjusted based on your age, your health, etc. You don’t have to do that now - you can just leave your pensions invested, and drawdown money whilst the rest still (hopefully!) grows.
I just looked at an annuity calculator on Aviva’s website. To get £7500pa for life from age 67, you’d need £135,000.
That’s just to give you a rough number. There are other options. And that doesn’t cover your age 60-67 period. Just things to get you thinking.