Land Drain to Combined Sewer

Hi all - we came very close to flooding recently in some very extreme weather - about 5cm from threshold at back of house - not from river but from rainfall alone - it was mad

We are on clay soils and when it rains the water just sits for ages and we havent got anywhere for the water to go

Ive thought of a soakaway but that will be sited too close to a boundary wall (which has just been built) and too close to the house too - plus as its clay - the water just doesnt go anywhere (ive dug fence holes and the water just fills up and stays for days)

Basically we haven't got anywhere for the water to go

We currently have a combined sewer and as the drive is currently broken up now and before a new drive goes in it would be a good idea if possible to put some drainage in

I know the drive people will have to put some drainage in too - probably aco drains but the way the drive will slope will mean more water will be directed to where we dont want it essentially (back of the house - the front section of house isnt a problem)

So ......I was thinking of 5m worth of french drain (wrapped in fabric) immediately outside the back of the house where the water does collect (this isnt having a drive laid on it too - will be decking over this bit)

.....then the french drain going into a gully pot with a riser (this will be sited ready for the new drive when its laid) Gully pot is to stop smells and rodding purposes mainly. From the gully pot then into normal solid underground drainage and then into the existing drain line using a y junction which eventually goes to the sewer

I know its a last resort and probably not even allowed to go into the sewer in reality but as it came that close to flooding the house I feel like we have had a warning and now is the time to do something about it - plus its also a combined sewer too and its only a small section of ground that we are trying to dry up a bit

Any advice on this is welcome - does this sound ok - just trying to stop house from flooding really

Thanks

Catch manhole. The water enters the top and then exits the top, any sediments settle in the catch manhole/ catch pit. Every so often, empty the manhole of silt.

Although it's a manhole/pit, there's no pipes at the bottom.