Have you asked the neighbours yet? It's impossible to say if it's a soakaway or not without investigating by some of the means already suggested several times over in the thread.
If the type and location of their gully looks the same as yours, could you, with permission of course, try putting a drain rod down their one and see where it goes?No neighbours have no idea.
Even if the bill is correct it may not be informative. If all the surface water goes into soakaways then you get a discount, but if any goes into the public sewers you don't. So, say, a soakaway at the rear and a RWP going into the public sewers at the front = no discount.Your water bill will state whether your surface water goes into the public sewer. Otherwise it will discharge into soakaways.
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