My Safari is a long, long, long way off being on the road, so went and bought this today;

(difficult to photograph a dark blue car in the dark
2.0 HDI (110 bhp) 151k, MOT till Sept, very little service history but I know when the cambelt was last done and it's not due another service for another 10k (last one at Wolsley House Motors, when it had new front pads, discs and particulate filter). It's also had a new exhaust since then.
LX but with hydractive3, brand new rubber boot floor liner, tow bar, genuine locking Citroen roof bars.
It also has new wind deflectors all round.
It was up for £800, I gave £650.
I'm a died in the wool green blood Citroen owner and have generally been unimpressed by modern ones (C6 aside) and a virgin to LDS so had a read up on here about C5's first
Having done a few hundred miles in this C5, I must say I have very much underestimated them...
Has a few problems though of course...
- Front suspension height needs adjusting (low is at low, normal ride height is at intermediate, intermediate is at high) Rear is all spot on and it all goes up/down smartly with no other problems
- Tacho and Speedo under read. When at rest, the pointers are basically pointing straight down. Speedo under-reads by about 15mph, tacho doesn't go above about 2.5k.
- Tailgate doesn't stay up
- Drove it back in the dark and very occasionally the headlights flickered
Any advice on those?
I've read that the speedo/tacho stepper motors can be a problem? How do I test if that's what's wrong, or if it's something else? Would it be usual for both of them to fail at the same time?
There is also a slight judder at speed or when pulling away hard. If this were any other car, I'd say it feels like engine mount to me, or tracking out which is exacerbated by the front ride height being over high. Unless there's anything else common on C5's I should know about?