Can I print "Black only on the Epson BX 300 F ?
Since the printer insists on having all 4 cartridges (non-empty) fitted before it will print anything, the only recourse to fitting new cartridges is to fool the printer into thinking your empty magenta cartridge has ink in it. You can do this by using a cartridge resetting tool to reset the magenta cartridge chip so it reads "full". A resetter tool can be obtained from e-bay very cheaply (£4 or less). You will find sellers who ship worldwide on E-Bay UK.
Be aware though, that if you forget to select monochrome printing, the colour ink is also used in black printing - and printing with a "dry" cartridge can damage the print head. You can guard against this by filling your magenta cartridge with distilled water.
You will also find sellers of magenta cartridges (and the others of course) on E-Bay UK who ship worldwide.