Blocked drain

[237SJ]

My mum has a little drain outside on her patio that the kitchen water drains into (a small drain with a grid) It`s blocked and overflowing onto the patio.
How do I clear it? Do I have to get some sort of bendy rod to prod about? I`m trying to avoid calling anyone out at the moment because they can rip you off.

[TonyV]

albags - indeed