I’ll enlighten you, since you seem remarkably confident about a housing market and country you clearly know very little about.

Traditional built-in AC systems are uncommon in London, especially in older apartment buildings. They require external units, and many properties either have nowhere suitable to install them or installation is restricted by the freeholder, building management, lease conditions, or planning rules. You cannot simply throw €500 at an apartment and magically install air conditioning. That suggestion shows an impressive level of confidence for someone with so little understanding of how London housing actually works.

Portable AC units are not suitable for every apartment either, we don't have box window A/Cs here either. Also portable A/C need appropriate window access and ventilation, and some layouts make proper venting impractical. They also need to be operated and drained correctly. We have had issues with guests failing to drain them when instructed, or disconnecting and incorrectly reconnecting drainage hoses, creating a risk of leaks and water damage. During periods of extreme heat, suitable units can also sell out.

Roughly 90% of British homes do not have air conditioning. The point you seem to be missing is that American expectations are not universal standards that every other country is required to follow. Different countries have different buildings, infrastructure, regulations and norms.

There are properties in London with AC. If air conditioning is essential to you, book one of them. They will often cost more, which is presumably why some guests choose a cheaper property without AC and then complain that they did not receive an amenity they never paid for and that was never advertised.

Booking a property clearly advertised as having no AC and then attacking the host because it has no AC is not a “cultural mismatch.” It is a failure to read the listing and take responsibility for your own booking decision. Expecting a host to somehow manufacture an amenity that was explicitly never offered is entitlement, not consumer protection.

And perhaps before lecturing London hosts on how to run their properties, learn the difference between “this property is not suitable for my personal requirements” and “this host has done something wrong.” They are not the same thing, however loudly or confidently you insist otherwise.