It is lovely to hear from you, and I would be more than happy to provide some reassurance and guidance for your specific setup.

To answer your main question first: Yes, the distance of the perimeter wire (if you choose a model that uses one) will be different for each side of your lawn.

The Block Paving Side (Level): Because the mower can safely drive partially onto the block paving, the wire is placed closer to the edge. This allows the mower to "overhang" the paving, ensuring it cuts every blade of grass right up to the bricks.
The Metal Edge Side (Raised): You must place the wire further away (usually about 26cm–30cm). This prevents the mower from physically hitting the metal edge, which could damage the blades. This usually leaves a small strip of grass that requires a quick trim with a strimmer.

My Recommendation for Your Needs
Given that you have a small area (40sq m), want minimal hassle, and travel often, here are the two best paths for you. I have replaced the Worx suggestion with the YUKA Mini, as it truly represents the "best" in terms of modern, hassle-free technology.

1. The "Simplicity" Choice: LawnMaster OCUMOW 16
Since your total area is very small, this is a great entry-level option.

https://easylawnmowing.co.uk/lawnmaster-vbrm16-review/

Why it fits: It is a "Drop and Mow" system that does not require a perimeter wire. It uses sensors to identify where the grass ends and the paving begins.
The Benefit: As a 71-year-old looking for simplicity, not having to install or maintain a wire (which can occasionally break) is a huge advantage. It is very much a "set it and forget it" machine for small, simple spaces.

2. The "Best Technology & No Hassle" Choice: Mammotion YUKA Mini
If you want the absolute best machine regardless of cost, the YUKA Mini (or the upcoming YUKA Mini 2) is the superior choice for your specific situation.

Why it fits: It uses RTK (GPS) and Vision technology, meaning there are no wires at all. You map the lawn using an app on your phone, almost like driving a remote-control car.

https://easylawnmowing.co.uk/mammotion-yuka-mini-review/

The Benefit for You:
No Wires: You won't have to worry about wire distances or wires breaking while you are away from home.
Multi-Zone: It handles navigation paths between two lawns perfectly. You simply "draw" a digital path in the app, and it will move between the two areas automatically.

Precision: You can digitally adjust the boundary to get as close to that metal edge as possible without the mower ever touching it.
Remote Monitoring: Since you enjoy time away from home, you can check the mower's status on your phone from anywhere in the world.

Final Advice
For a 40sq m lawn, the YUKA Mini is technically "overpowered," but it offers the most "hassle-free" experience. You won't have to worry about different wire distances on the raised metal side versus the block paving side because you control everything precisely through the digital map.

If you want the absolute best and most reliable setup that allows you to travel with total peace of mind, the YUKA Mini is my top recommendation for you.

Selection tool: https://easylawnmowing.co.uk/find-the-best-lawnmower/