Are you able to get to the top of the bank, if so you can lower a mower on
a
rope! works a treat. Otherwise it may be a case of weed control fabric
and
vigorous climbers (Honeysuckle for example) to foliate it.

I can get to the top, but I couldn't lower a petrol mower due to the
steepness and too far from electricity.
It's about .5 acre so weed control matting would be far too expensive.

Thanks
Jan