Well, not knowing what kinds of mowers they sell in your area, and thinking you don't want to, or can't, here's what i'd look for:
A self-propelled 3-to-5 h.p. 24 to 30 inch cut. mower. (Note: I do not use metric, nor British measurements!)
Grass catcher optional. If your are going to mow to the Queens standards, better buy the self-propelled. If just for yerself, play yer hunch! HTH: Rusty Jones

I would recommend a Toro Super Recycler but I do not know whether that is available in your area. Any good mower can be made to last for years if proper maintenance is performed and if problems are fixed rather than deferred.

I've been using my Honda for 23-24? years now.
Just a few air filters, spark plugs & blades have been needed, although I must admit there is a good amount of duct tape on the bottom of the bag.

Most of longevity is good maintenance!

I have, and regularly use, a 25 year old Snapper and a 20 year-old Gardenway Troy Bilt (note that this is NOT the present-day manufacturer of Troy Bilt equipment). Both machines were priced at about the median range of self-propelled mowers. Both have Briggs and Stratton engines. CAREFUL MAINTENANCE IS WHY THEY'RE STILL USABLE MOWERS.

Some of the major "proper maintenance" items are: Keep the oil reservoir filled; Change the oil at OR BEFORE recommended intervals; Keep the air filter clean; do NOT let gasoline sit in the tank and carburetor (particularly if it contains ethanol); Change the spark plug each season. Also, run the engine at wide-open throttle; this keeps the engine properly lubricated and also maintains the blade RPMs at the correct level - you are NOT "saving" your engine by running it at 1/2 or 3/4 throttle. (If your engine has pressurized lubrication, the open throttle is not required for lubrication, but it is still needed for blade speed.)

And by the way, my 90-year-old father-in-law has a 20 year old Murray push mower, with the bottom of the line B&S engine. It is still in regular use. This is ONLY because he does all the recommended maintenance, and when something breaks he fixes it with the correct part.

If I were buying a new walk-behind mower today, I would look first at the Honda.

Since Kee is no longer available I would look at a SARLO Diesel walk behind. Cheaper to operate, in the long run. Kind of like a Parrot, it will out live you and your kids. Better put it in your Will. It has a large rear 20" bicycle wheel for balance and easy control. Belt driven to protect the engine from sudden stoppage damage American Made in Ft. Myers, Fl. You buy it directly from the manufacture. And the way ethanol and gas fouls up so quickly diesel is looking better and better each day. By the gallon diesel is higher but the SARLO runs on 1 gal / 8 hour day.

I second the Honda. Nearly all of the lawn crews I see use them for their walk behind.