Forgive my ignorance, but why would you want to use a double rifle on UK deer species?
For the pleasure of it, for self-indulgence, to experience equipment at its acme.
And, maybe for the same reason, last year, I bought myself a Boss. And, oddly enough a Baikal IJ-28. Both, in their own ways, "enjoyable" as both are the "best" of what each of them represent.
To realise a wish that has become attainable. Or just because, in three words "And why not?"
I shoot and I fish because I like it. I don't need to do either. Sometimes I "bag", sometimes I "blank". But at least if I "blank" with company that I enjoy and equipment that I pleases me them I've still had a day that I'll cherish.
If I just want to "butcher" deer I could simply save money and get a plastic and stainless Remington 700 in .243 and stick a moderator and a Leupold 4-12x44, or whatever ridiculous magnification, and a "tactical" reticule, 'scope on it.
Or, for the birds, a bloody Beretta...well designed, absolutely given the heritage of it's design, and 100% reliable, yes, faultless in fact, undoubtedly, but, also with it, mass produced, characterless, bland.