Without a doubt, my lovely(ish) 205D-Turbo. It was quite economical and surprisingly pokey as well.
I spent quite a bit of time sorting it when I first got it cheaply (twas £100 as the h/g was in urgent need) and did all those other little jobs while the head was off too such as cleaning and repainting the inner wings. I also drilled out the small return hose on the thermostat housing as on these they tend to clog.
I remember changing one of the coolant hoses and it was a pig

as I had to take the inlet manifold off for access to the lower end. oh well.
Had 306 'meridian' alloys too which seemed to suit it reasonably well and were sensibly sized, the offset was near enough too.
The downside was the GTi front suspension as around here there are a *lot* of those square speed bumps and I had to go over half a dozen each way to work and back and anywhere else, no choice. This did not assist the life of the wishbones, typically they would want changing every 2 years however I did use pattern ones as the genuine ones were about 130 odd each, and pattern ones were a more wallet friendly 45 or so from what I recall.
Other "unusual" changes I made were to fit a diode across the instrument panel so the coolant level light illuminated with the oil pressure as a 'test' so I could be sure it worked. Surprised they did not have that anyway.
Oh it had the 'back of block' fuel heater as the 205TD's do not have the "top hat" fuel filter as its not possible to fit it due to hose incompatibility on the turbo (as the NA does not have an oil cooler so it does fit that) , anyway the 'back of block' heater did its usual trick of being more interested in taking in air than anything else, so it was bypassed and after some thought I made a fuel heater using the thermostat return pipe (which gets hot first) and the fuel inlet pipe. I used a few inches of microbore central heating pipe for the fuel line and normal copper piping for the water return. These were slightly squashed to give htem a flat side then scoured and soldered together. Result was slight warmth but not enough for it to be a problem. It was fine like that.
The other change I made was to replace the fuel filter housing as it started to take in air as well, I found a generic one with a sensible spin on easily available cartridge (similar to the TUD's actually) with a built in primer, piece of cake really. You can see that in the fuel heater pic.
It was a H plate, had the full black dash, and lovely dark grey velour sports seats, along with the GTi style instrument panel (I know Jim had an STDT so he'll know what I mean) same thing but in black/grey rather than most STDT's which appear to be beige inside.
I do remember the radiator being quite expensive (approx 130) simply as the DT's had a different one, limited market I guess. Body parts were cheapish and engine parts were cheapish but anything specific for that engine in that body was not it seemed. Hmm. My conclusion anyway.
I was planning on fitting an intermittent rear wiper (easy with a 306 relay actually) but never got around to it.
I also swapped the front seats side to side as the drivers bolster was a bit floppy (oo er!) , quite easy you just have to swap the frames over as well carefully to retain everything.
Spec was not too high:
No PAS (sadly)
It was a 5 door (I would of wanted a 3 door if there were choices personally)
Central Locking (not remote, too old for that)
Vacuum sunroof and no leaks or issues at all.
A few pics, I do not have many:
A nice car (although it was a random pic, it did need a wash)
Factory Fitted Instrument Panel (It had just under 200K on when I got rid) 205 dervs with factory tacho's seem to be like hens teeth
Fuel heater pipe work
