A4 B7 3.0TDI Gentle Regen to fix the common the faults

So my 2005 B7 Avant has clocked onto 126k this week. And I'll take that as an excuse to treat it to a few fresh parts. The car already sticks like glue to the road (Thanks partly to good Pirellis), but my aim is to refine the ride. Make it smoother yet handle the bends a little more square. I am in the middle of getting a bike license, so cost has to be considered. Any suggestions of where i can go to the below points done properly without paying stealer prices? Thinking of using a company caller Neil Garner who are a race team, but open to suggestions.

First part - Oil & Filter - 8L of Castrol Edge Long Life 5W-30 - (£70 for Oil)
Air Filter - Bosch - £10
Front Suspension Link Set - (£240)
Rear Shocks - Bilstein B4 - (Rear £75)
Brake Hoses - Brembo (£34)
In flight entertainment - XTRONs head unit PB78AA4RIP - £310

Any other suggestions?

What are peoples thoughts on refreshing the diff oil? As my rear diff is weeping slightly (supposedly a quattro thing). How often should these be refreshed?

I have the standard P2021 code for the swirl flaps. It just flew through it's MOT with no issues with emissions. You can see one of the sensors keeps trying to find it's full extent. Has anyone recently solved this?

Flickering Xenon light? Another common issue supposedly. My brother had it on his 3.2L A4 Cab. Any suggestions?

Its the beginning of a gentle exfoliation for the old girl. Make her feel more special.

Also, can anybody suggest someone to replace the TPMS sensors on the car? I have the warning light keep coming up and since the wheels have been refurbed, it's just an annoying warning every time i get in.