Well, Ahmed, it's worth thinking about what you are actually buying when you sign on the dotted line for a bolt-action rifle from one of your named gunsmiths.

The barrelled action will have come from FZH or Mayfair Engineering. The engraving will almost certainly have been outwork. The stocking may be done in-house but, as I understand matters, Boss outsources all its work.

What you are being sold is some vision of gnomes painstakingly manufacturing your hand-built rifle, and what you are getting is a very nicely-finished after-market Mauser 98 action. The one area where it should shine is fitting.
I do not believe that the position is substantially different with double rifles. Most of these, I strongly suspect, come from Mayfair, but in any case the actions are coming off CNC machines rather than some old fart in Birmingham patiently filing down lumps of metal.

All of these elements are reproducible by an individual buying his own action in the white and then hunting down his own engraver and stocker/ fitter. Your finished product won't cost anything like as much as a New Holland/ Purdey/ Boss, and nor will it have the same aftermarket value, but it won't depreciate as much either. It ought to be just as accurate and good to shoot, though.

An engraver that I can recommend is Andy Miles, who works for all of the London gunsmiths. I use a stocker in Poland called Arek at Top Gun.

In the alternative, you can go to someone like Paul Roberts, of J. Roberts & Son. He used to own both Jeffery and Rigby, so he knows what he is doing. You will get a Jeffery or Rigby equivalent, but without the magic name engraved on the barrel and - at a guess - at at least half the cost.

While on the subject, you should also look at the accounts - using the link that I posted above - for the London gunsmiths. Purdeys and Hollands are losing money-hand-over fist - arguably this makes their rifles very good value for money, as they are being sold at a loss! - and Boss looks to be in a particularly hard place (I understand that it has recently changed ownership, again).

I would be very cautious about entering into a long-term contract to buy a rifle from any of your named lot. At a minimum, I would insist that any money paid by me was paid into trust for my rifle and not intermingled with the companies' own funds. I would also insist in paying in arrears.

The two companies which do seem to be doing very well are Rigby and (in Birmingham) Westley Richards.

Finally, I would question just how much your grandchildren will benefit from your collection. On the assumption that you bought them new, you will have already suffered some pretty severe depreciation. So far as I can see, both Purdeys and Hollands are very shy about the cost of their (new) bolt-actioned rifles, but I would suspect somewhere around Ł30,000 + VAT. Big bore rifles in the northern hemisphere typically do not get a lot of use, so it is possible, with luck, to pick up good rifles second-hand at a good price: my H&H .375 takedown cost me approximately Ł7,000, and my Jeffery .404 a scarcely believable Ł1,100.