Just to clarify you have a separate Humax freesat box, or are you saying the TV has an inbuilt freesat tuner?
Assuming there is a separate freesat box, we should start by powering it off for a minute, then starting to back up encase it has frozen.
If after restart the remote still doesnt work, we need to check the tuner\box isnt faulty, are you able to change channel using the buttons on the device itself?
Assuming the box isnt faulty and you can change channels without the remote, the next stage is looking to source a replacement remote, to find you a suitable remote can you please provide me with the model number of the Humax device.
The boxes are not designed to be left on standby for weeks\days on end, they often just get confused over time.
Powering off the TV and Sat box at the wall once a month is always good practice, you often find they work abit faster too.
Appreciate if you can rate the service received today so I can close the case.