Try one of these - a 505 Gibbs semiautomatic - well over 5000 ft/lbs of energy with an accurate range of well over a mile. Should sort out charging Muntjac for any bdy who feels a wee bit undergunned.
Have a look at www.vigilancerifles.com for more info!!!
And you can moderate them so you don't wake up the neighbours.
Not sure if Home Office would look to kindly, given it is a semiauto etc - but you could always move to the continent where such things are allowed.