Which MS Office is most suitable for me and my family?

here you go.

1) are there different versions of Office for Apple vs PC products?

Yes, difference is minimal.

MS Office for Mac: fully compatible with macos and includes word,excel, powerpoint, and outlook. The interface looks slightly different from the windows version, but the functionality is very similar

MS Office for Windows: Similar apps but better integration with windows features like file explorer and certain keyboards short cuts

File Compatibility: file created on either platform (eg: .docx, .pptx) can be opened and edited on the other with out any issues

2) which is the most up to date version I can get of Office?  (Based UK).

The latest perpetual (one time purchase ) version is MS office 2021 home & business . it includes

.Word, excel, power point and outlook

.A one time payment covers the license for life but you wont get feature updates security updates

Microsoft 365 Family is subscription based option that gives onoging updates and additional features, but since you prefer one time payment, above option is choice for you. its up to you. i personally using 365 Family vesrion for entire family. can share upto 5 members, 1 TB space, Copilot, teams..etc

3. are immediate downloads online ok?  be cautious here, as this where many people run into trouble

Safe sources:

Buy directly from microsoft website

Truested retailers like Amazon, john lewis or Currys on the UK

Avoid 3rd party or discount sites

Download process: if you buy from a trusted source, an immediate download is fine. 

Though you have outlook, when you buy, you will get everything as per pack :-)

Based on above, you can decide either one time or family version. hope this will help for your purchase.