given the mileage you have had from your current headset, i would look to buy cheap
£10-15
if you want a white stem, then just get one to suit your current bars.
if money isnt a consideration then you want a cartridge bearing headset, new stem, new bars, might look at replacing those old shifters and grips and essentially those brake levers are just gonna look plain old, so new brakes too, of course most new brakes will cause you some problems with the fittings on your fork, but that fork is long overdue a replacement, since you are taking out a loan you might as well chuck in a full 1×10 drivetrain and some decent tubeless wheels, on Hope Pro3 evos, natch.
now about that frame, wouldnt you be better suited to a prince albert classic?
keep the saddle tho.