If it's mainly for use at home, 17" is OK, but it's somewhat big and heavy to take with you taking the underground to and from your work everyday.

Personaly, I have a 15" Dell Precision laptop from work, but I and most of my colleagues use it at work with a separate monitor (4:3, not 16:9), and a (wireless) mouse and keyboard. so that laptop is used as just a small desktop that you can take with you to a meeting or home (and, yes, I use it with monitor, mouse and keyboard also at home).

Using a VPN to work is just software and works on all PC's or laptops, provided work offers it.That's a question for the IT dept.

Using Excel (and mail and browser) is only a basic task for any modern laptop, so quite unsuitable as exclusion criterion for any model. But he might prefer a 128 or 256 GB SSD above a 1 GB HD, and that makes it somewhat more expensive. Presence of at least 2 USB3 ports and HDMI out can be considered standard nowadays, so that will be easy.

If it's for work, it's pleasant to buy a laptop that comes with a 3 year next working day tech service at home or office. The usual consumer grade laptop - when something is wrong and it needs repair - easily takes a takes a few weeks to get back.

Kees