There is no H4831 available in UK dealers - none has arrived here from Hodgdon for a year and none will arrive this year, very likely during much or even all of 2015. That applies to all Hodgdon powders manufactured by Thales / ADI in Mulwala, New South Wales due to severe sea transport problems. That's H4198, H322, Benchmark, H4895, VarGet, H4350, H4831/4831sc, H1000, Retumbo and H50BMG under the Hodgdon name plus IMR-8208 XBR in the IMR range.
Hodgdon ball technology powders (manufactured in the USA) will continue to be supplied: BL-C(2), H335, CFE223, H100V, H414, H380, LEVERevolution, SUPERFORMANCE.
Also, Hodgdon is trying to make up the shortfall in the ADI powders by substituting Canadian manufactured IMR grades wherever possible: IMR-4227, 4198, 3031, 4064, 4895, 4320, 4350, 4831, 7828/7828SSC.
Possible alternatives to H4831SC include Viht N160 (considerably faster burning), N560, N165; IMR-4831 (faster burning, NOT a straight substitute); Ramshot Hunter and Magnum, Lovex SO71, Hodgdon SUPERFORMANCE, Nitrochemie 'Reload Swiss' RS70 (due along with other Nitrochemie powders to be launched in the UK late this year).