What should I focus on in terms of maintenance?

So here is my pride and joy, '03 530d auto. I bought her 2 weeks ago for £1600 at 164k miles, and now she's now happily sitting on 165.5k miles. She is an absolute joy to drive, and came with a very comprehensive service history from the day she came out the factory, with full receipts (£7,199 worth of work) to verify every job that has been done. On the day of purchase, I spent 3 hours logging every receipt and cross referencing them to the MOT history and everything checks out (for example failed MOT one day for screen wash leak and OSF coil spring, then passed the next day with no advisories and the receipts for a brand new screen wash pipe and OSF coil spring). So it's safe to say she has been very well looked after, and should be in very good condition. The only issues I am faced with is a bit of surface rust on the sills, bubbling on the bonnet, and the engine temp fluctuating once it gets warmed up (probably secondary EGR thermostat).

I have included the spreadsheet so you guys have an idea of the type of work that has been done over the last 165k miles, so based off of this, what preventative maintenance should I focus on over the coming months, in order to prolong the life of this car as much as possible (as I'm planning to drive her until the government makes it impossible to daily an old diesel). The previous owner assured me he carried out oil changes every 6k, and the last oil change was 500miles before I bought it, as was brand new copper brake pipes all around, brand new front brake calliper, discs, and pads (which he showed me all the receipts for).

Apart from the obvious, 6k miles oil change intervals, and full service annually, what else is there that I should turn my attention to?

(I've seen talks online about turbos going bad around 150k miles, the autobox needing a service, despite being lifetime, and oil breather pipes needing replacement, but I'm not sure on these).

It's also probably worth mentioning I'm planning on getting a downpipe, straight pipe, deleting the EGR and swirl flaps, and getting a tune, once I'm confident all the necessary maintenance is done, and there are no weak spots.