droopy,
most of that is easy fix's fella,
the suspensoin noises are prolly Arb drop links, £30 ish from ecp/GSf,
Hp pump clicking all the time could well be tired accumulator sphere, £20 to fix,
rear lights = poor/bad earth behind the lights, pop them off form inside the boot, clean up earthing point, wire brush contacts, sorted,
also worth doing is to open all the plastic block connectors int he engine bay (big one under the battery) give them a clean up, light smear of vasalene and cabletie back together, and check the battery to chassis and battery to cog box earths, that will help most eathing issue's.
interior fan is most likely the controller in the fan unit under the bonnet, can be bridged on the fan board inside the car to make do (had mine for a while with a switch fitted nicely in the vent to bridge it and keep it going!) tenner from a yard for a complete blower unit,
fans not cutting in could be just corroded wiring by the fan switch in the rad pipe, (bridgeable to check fans work), otherwise, 5 minute job to wire in a switch to override the fans!
and i'd hazzard a guess that the brakes and steering is mainly due to air in the system, and lhm flush and bleed will prolly sort it!
all in, weekends work tops which for a 20 year old car, aint bad to get her sorted!
as for what to do with it, entirely up to you! if you want to do the lump out in a 205, then do it, but its So old hat now, its barely worth doing!! gti-6 lump is a better option! end of the day, not many cars can give such a grin enducing Drive and also be a very good Super comfy Cruiser!
no one expects a BX to be quick, and most peopl eout there inthier saxo's etc. havent got a clue what it is!!
but, its your car to do with what you please!
me, i'd spend a weekend tinkering and be sorted!!