Right so word processing, browsing, email, and some other office suite activity. No intense VBA or anything like that, no gigantic spreadsheets, no video rendering, playing computer games that require a discrete graphics card.
For what you’re proposing you can spend anything from £300-£1,500. The cheaper it is the heavier it will be and the less time it will last.
If you’re used to macs then I’d suggest staying with them. Most people who use PCs aren’t comfortable with the 6-monthly format that is really required to keep them running smoothly. Also, cheaper PCs (esp dells and acer’s come with terrible bloatware).
I would recommend a bottom of the line MacBook. They’re £1,249 but if you have a child with a student card you can get a 10% discount. They come with a 256gb internal SSD which is loads for your purposes. The graphics isn’t quite as powerful as the pro, but you won’t need it. It will do everything you want, is light, and will be good at what it does for the next 5 years.
You could get a windows laptop (I have one myself), but unless you’re prepared to spend a great deal of time configuring and really setting it up, and redoing that every 6 months, it will slow down and really start to piss you off. It will also start to slow down considerably anyway around the 2-3 year mark.
You could get a windows PC and put a Linux based Graphical user interface (like gnome or whatever you want to use) on there so it acts like a mac, but it’s a v steep learning curve. This is, however, the cheapest most effective option.
If you’ve got £1,200, a bottom of the range MacBook is what you want. It’ll be good for 4-5 years. It will work and you’re already used to it. Spend more and you’re getting features you don’t need. Spend less and you’ll have to work for the same functionality. If saving money really matters then a windows PC with 8gab+ of RAM, an i3, i5 or i7 latest gen intel processor and a 256gb+ ssd is all you require in terms of hardware. Those specs will be cheap to achieve, but to make them work nicely is either effort (Linux based GUI) or cost (mac, with macOS, which is also a Linux based GUI).