Electrical duct rise through slab

I need to get a power cabling route from a distribution board in a new extension to a shed and garage outside. I don't want cabling or ducting visible outside.
The issue I have is the builder has put drainage services on both sides of the wall. (see sketch below) - the screed and insulation has yet to be laid - this is the only issue holding things back. I think my only option is to core drill at an oblique angle (once I've established the exact depth of the external rainwater drain).

Does this sound feasable? Any tips of angled core-drilling (given I've only got a handheld drill)..?
I'm not certain on the size of duct/drill yet, it's most likely a pair of 4mm swa, inside whatever duct will allow me to pull that through without grief - probably 50mm twinwall
As I'm penetrating the DPM there'll have to be some significant repairs I was considering denso tape and then black-jack paint over the top - possibly overkill - but would it pass muster?

Obviously externally will be afforded the usual protections, sand/tape etc..

Ask the spark who’s doing the work ?

Murdochcat said:

Ask the spark who’s doing the work ?

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I don't see why it takes an electrician to drill a hole in a wall.

DetlefSchmitz said:

I don't see why it takes an electrician to drill a hole in a wall.

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They will be able to advise what they would prefer

I’ve had customers think they are helping out and do things without asking and it’s not helpful

could you take a brick out below the outside dpc and another above the internal dpc and drop down in the cavity?

Murdochcat said:

Ask the spark who’s doing the work ?

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Spark isn't interested in drilling a hole, and has offered a price for the job in the expectation the site is ready for a cable to be pulled and terminated with no messing around.