Not necessarily - the input will need calibration in any case, and I don’t know the availability of components in Nigeria. Headroom isn’t a problem - the 1.5 kΩ will give well under 1 V even with the UK adapter. A metal film resistor will probably come as 2% or 1% in any case, viz: http://spiratronics.com/0.25w-metal-film-resistor-1k5-pack-of-10.html.