Since every one is adding their internal (and why not external too?) modifications, I might as well add mine.
1. Glove box cover, easy.
2. Sound insulation on the floor pan, door sides, wheel well, engine bay and engine cover, xtra plastic wheel arches cover over the rear wheels (good effect). The car is really quiet! It is a difficult procedure, takes time.
3. cold air intake engine. I don't know if it makes a difference, more like snake oil!
4. Sony stereo 1-din with blue tooth and sony speakers 2 of them on the front doors and Hertz speakers 2 of them on the dash.
5. reverse parking sensors with distance monitor in meters (not just few beeps)
6. Extra driving lights, in phase with high beam.
7. Rear door opening internal coupe light activation switch.
8. Baggage room light, Philips LED light with movement and night sensor. Easier than the glove box cover fitment and very useful too. Runs on battery. Lasts more than a year.
9. Extensive rust proofing in all hollow rooms (door, frame, door sill, frame etc) and under body coating. Just had MOT inspection yesterday, the rust proof coat still looks good after 8 years. That was a difficult procedure.
10. New brake discs and pads on the front wheels a few years ago.
I do my own service once a year, oil and filter, air filter change, AC filter change, inspection etc.
This is one hell of a cheap car to maintain and gives you the economy and driving pleasure that no other car matches.