Something to try - if your Humax box is anything like mine, it probably has timeshifting enabled. This is basically live backgound recording of the current channel, so that you can pause and rewind live TV. If the HDD has a fault, it is likely to cause problems with timeshift, which could manifest in freezing etc. If enabled, try disabling timeshift to see if this improves the functionality of the box. This may allow you check the integrity of your recordings and plan your next move.
If the HDD is in a sorry state, then it is likely that the cost of professional data recovery would far outweigh your desire to save recorded material. If you're lucky you might be able to hook it up to a PC capable of reading Linux partitions, but this is likely to be slow and painful and recovered files may well be corrupt.
Personally I would just stick a replacement HDD in the Humax box and format/initialise via the Humax settings menu, and write the old recordings off.