5W-30 is a bit low I would have thought. 10W-50 would be a better choice; that turbo can get quite hot (so 40 or 50), and I don't think you need to go as low as a 5W in the UK. - I'm sure oilman will correct me if I'm wrong.
There aren't many weekends left before Christmas. Is your car on the street or in a garage? Maybe I
could drop in on the way home if it's gonna be warm and well lit... I have a picture to help anyway.
The oil pressure sender is that big bit sticking out with a black wire to the right of the oil filter, just below the PAS pump.
If you want to get at it with the engine in, I'd put the driver's side on axle stands and take the wheel off - you should be able to reach it through the arch.