That's fair enough.
I've had nothing but trouble with Windows in the past.
All my gear now is Apple (past 5-6 years) and everything still going without a single issue. Might just be lucky?
I have no experience in which machine works best in an office environment, so OP should ignore my first post.
A Macbook Pro for around £1000 will last at least 5 years and won't break unless you throw it off a roof.
It won't really slow down.
Any other laptop will probably have severe issues within 5 years, will definitely slow down and will likely chuck itself of the roof just to end it all.