Oil and Water leaking from 2014 3.0 TDI

I need some help.

I have a 2014 Audi A8 which is fitted with a 3,0 TDI engine.

The car has been loosing water intermittently from about 4 weeks and now has started leaking oil.

Within a fews days the car will consume 1 litre of fluid however although there is a strong smell of boiling anti-freeze there are no external signs of the leak. The oil is very visible on the front of the engine and on the back of the radiator. Initially the oil was concentered on the off-side and then after performing a steam clean today it is now centred on the near-side. The oil that is visible looks clearly dirty, however the oil in the engine is only 50 miles old. Finally, the heater in the car seems very sluggish and about 18 miles needs to drive before the heater creates any real heat. A new oil sensor was fitted but made no difference.

My garage are really struggling and I am desperate for some advice.

Thank you so much for offering help - really appreciated. I will get the T pieces checked. The oil leak is serious - on a 20 mile journey probably quarter of a pint was sprayed across the front of the engine and Rad. We changed a suspect sensor but this failed to fix it. There is no obvious source of the leak on the front of the engine. Even when we stream cleaned the whole engine we would not spot where the oil was coming from. I am starting to think it might be the oil cooler as this has oil and water flowing through it. The garage will remove the inlet manifold tomorrow and check whats happening underneath. Thanks once again for stepping up.....