Welcome to the forum. Sorry it has taken a while to get reply, but there aren't really many active users left on the forum nowadays.
The upper dash strip (above the glove box) was a carry-over from the earlier bubble Rover 200 and was finished in a Walnut effect pattern on the Rovers and a printed silver carbon fibre effect pattern for the MG ZR. Revisions to the dash for the 2003 model year saw the dash moulding altered and the trim strip deleted for both the 25 and ZR. As it fits into a recess in the original dash moulding, and the revised moulding hasn't got this, it isn't really possible to retro fit the dash strip without swapping out the entire dash moulding (although this isn't actually as big or as difficult a job as you might at first imagine).
The painted door pull inserts and heater control fascia may well have been painted aftermarket, but these parts were actually available as a brochure listed option for the early ZRs, and were subsequently offered as an option through the Monogram special ordering scheme which was introduced in 2002 (and offered a range of non-standard exterior colours and various interior and extra equipment options not available from normal dealer stock).
As you also have the steering wheel with the blue inserts (which was a similarly listed option), I would think they may be original fit. Some owners did retro fit second hand coloured steering wheels, but the blue ones were very hard to get hold of other than buying a brand new one from a Rover dealer (which were very expensive). On the earlier cars, a dash strip in the same colour came as part of the optional kit.
These trims were available in Trophy Blue, Trophy Yellow, Solar Red or Le Mans Green and were quite rarely fitted, and even rarer to find now.
The Monaco seat coverings with the coloured inserts (Blue, Red, Yellow, Green or Grey) were standard fit to all ZR 160 with the coloured inserts either matching or complementing the exterior colour. A different one of these colours from the one normally supplied with the particular exterior colour could be specified as a factory order option.
