Engine oil low pressure issue

Hi Guys,

I have recently bought an Audi a3 1.8tfsi 2014  no issues for a month then all of a sudden a warning light ‘engine oil low pressure switch off the engine’ appears.

1st visit to the local mechanic: oil change, oil filter & worked for a week then again sign came up.

2nd visit to the mechanic: a switch replaced for the engine oil pressure as it was broken, checked pressure in the oil pump it’s fine, cannot see any leaks, works again ok for a week and again the light comes on.

it only seems to appear at low revs going through slow moving traffic once I have been driving for 30mins plus.

my local mechanic has advised to book it in with Audi direct or an Audi specialist, I have suggested to change the PCV valve and engine oil pump but any ideas or Audi independent garages you recommend in West London.

thanks 

Vijay