Definitely a Homer Simpson 'DOH!' moment.
I was so fixated on that sump plug on the rear of the sump that I failed to noitce there was one up front!
That came undone nice and easy so oil change went ahead.
Did the filling up of the filter bit, only about 3/4 so I didn't spill any when installing it.
Prior to that I had carefully emptied 1/2 litre of fresh oil out of the can so I knew I would only put in the required 4-1/2 litres.
Took the fuel solenoid lead off and turned it over for about 20 seconds, get the filter completely full, lead back on, started up and let run up to temperature.
Checked underneath, no leaks, checked oil cooler assembly, no apparent leaks, so I would say good to go for the ITV tomorrow afternoon.
So I now have a miniature Homer stuck on the dash!
Happy days.
Jon