This is worth repeating. OP - make sure you understand the 4% rule thoroughly - I love that article, but make sure you understand the basics first.
4% is an accepted rule of thumb for estimating how much you can take - allowing for increasing what you take with inflation to keep the same spending power - such that it will last 30 years. ( Ie in 30 years time, the capital will all have gone too.)
People on here have talked about taking only the returns, but they often underestimate the significance of inflation over the length of time you are retired for.
Inflation is currently 4%. If that holds (not showing signs of going down) to buy the amount that £10k buys you today:
n 10 years - when you're 60 - , you'll need £15k
in 20 years - when you're 70 - you'll need £21k
in 30 years - when you're 80 you'll need £32k
In 40 years - when you're 90 - you'll need £48k.
Or to put it another way, if you think "I need £10k per year on top of state pension', and you use that number without considering inflation, when you're 90 (1/3 of women willl live to 90) then you'll only have £2k per year spending powerr, not £10k.
So back to the 4% rule: if you start taking £28k per year now, adjusted for inflation to keep the same spending power, you would expect that by the time you're 80 the money will be all gone. (The large majority of people currently aged 50 in the UK will live past 80).
It definitely doesn't seem enough to retire immediately aged 50. It probably is enough to retire a bit early - exactly how early depends on what your DH's pension provision is, as well as the standard of living you hope for.
https://www.retirementlivingstandards.org.uk/
What have you done with the £700k just now? I'd say that your priority just now should be investing that appropriately, based on your retirement timeframe. You should definitely speak to a financial advisor.