Hi Ricky,
Do you know where the nearest manhole is - & can you lift the cover?
The gulley trap and/or the gulley drain pipe are blocked.
Wearing rubber gloves or gauntlets you can reach into the gulley and clear it of debris and water.
The gulley drain pipe might Tee into the soil pipe thats draining the vertical S&VP (soil pipes dont enter gullies, they are separate from waste water) or it might run independently to the nearest manhole?
I noticed a bit of bushy debris that had maybe been removed from the gulley drainage previously?
Did that bushy thing (it looked like roots) come from the gulley? Or was it simply a dead bush?
After the gulley trap is cleaned out then, If you can get the angle, Rods will probably clear the gulley drain pipe.
If not you will have to work back from the nearest manhole.
I'm on my dinnertime now but there are a number of other issues that I'll comment on this evening if you want?