Classic fuel pump symptoms. Amazon has genuine pumps silly cheap at the moment:
VDO 405-052-002-001Z. Delivery is a tad vague for some reason, but probably still faster than Autodoc and 2/3rd the price.
You might want to get it recovered to an Audi specialist who will do it properly. Random all-makes garages have a habit of bodging and ruining D2 fuel pumps by fitting whatever incompatible crap their local factor has on the shelf.