any good gunsmith will make you a fantastic gun if you pay 150000$ like Holland&Holland get.
There exist some fine german big bore doubles, making for dealer like Manton or Jefferys and they are good as any british gun but that is not the question.
There are reason's: practical and econnomical is and was the double gun allways a gentlemans gun. The common hunter in africa and india was hunting with a inexpensive Martiny rifle till german know how give him the mauser rifle in his hands.
The brits build fine guns with mauser actions but this was allways for gentleman. Take a look into the 1925 Mantons price list. a original Mauser in 10,75x68 cost 220 ru. when a .416 Rigby cost 1275 ru. .
In action will be the rigby worth to pay the price of 6 mauser rifles. You will say of course yes but you pay old guns for a price you will never get it new made.
No ,the common hunter take the original mauser and was very happy with it. All the brits can do was only cosmetic. without the german actions ( like in booth world wars) they are nothing. Its not that I cant seen what for a fine cosmetic it was. But if you ask if the germans take over the market for big game rifles with time I have to say yes.