1101:

 

Given he cant get a good signal through the floors..
how could mesh be considered as a workable solution , if the nodes cant get a good signal it wont achieve anything  (?)

Perhaps separate ADSL into each apartment would be worth looking into (if possible). Then one aprtments bandwidth hogging wont effect everyone
else .
Does each apartment have a separate ph line ?

 

"I guess this is easily fixed with a wall-mounted locked box for the modem/router..."
yes, because otherwise you have someone trying a hardware reset on the devices .

 

I don't believe so and installing such just for ADSL would be a prohibitively expensive option.

What I am trying to achieve is a reliable signal that can be used in each apartment, with some future-proofing incorporated in the present day solution - we can wait until there's better Internet in the area before we start thinking about spending REAL money.

Not too concerned about one or other apartment hogging the bandwith - this is a holiday destination after all, with far better things to do than cruise the interwebs all day 

Currently leaning towards the Ubiqiti UniFi UAP-LR or the Ubiquiti UniFi UAP-AC-LITE as suggested by posters above (with more lean towards the UAP-AC-LITE, since that appears to have a higher output and Gigabit LAN)...