And it's sorted. Did the rocker cover again as the back of the engine was still soaked, along with the Vanos and currently at 850 miles with no oil light on and little change on the dipstick. I also swapped to Valvoline 10/40 for older engines which may have helped. Never been so glad. Overall the engine maintenance since buying from the old owner so far has been :

• Oil housing gasket
• CCV Valve and hoses
• Vanos Rebuild
• Rocker cover gasket
• Intake boots as a smoke test showed they were perished
• Expansion Bottle and low pressure 1.2 bar CNC milled cap
• DISA rebuild
• New Thermostat housing

Of course a lot of this isn't related to the oil leak, but I was surprised at how little engine maintenance was done before I bought it.