"Timothy Murphy" wrote | Mine are sash windows in a listed building. | I'd have to get planning permission to change them.
Wood box and sash windows are traditional in Scottish tenements (up to 10 storeys in parts of Edinburgh) and are cleanable from the inside. The top sash is cleaned by lowering it and reaching over the top of the sash from inside. The bottom sash is cleaned by removing one of the side beadings (on my windows they are hinged to allow this) and swinging the bottom sash in about halfway. There are brass slotted hinges on the box to hang the sash on.
Do you have the whole of a four-storey former orphanage, or just a flat? Either way, might be worth considering a window cleaning contractor every quarter with a cherry picker to do the whole building.
Owain