****reasonable choice of legal weaponry, including Accuracy International sniper rifles if you have £23K to spare....****
Reasonable choice would be $300 and “face to face” transaction....without government. 23K ($32,200) is not “reasonable”.
Accuracy International full-on military sniper rifles are not cheap. How much would one cost in the US?
.308 is £3,375:
ACCURACY INTERNATIONAL AT .308 / 7.62X51 BLACK FIXED STOCK RIFLE
OTOH you can get less exotic rifles for a lot less.