(1) Please might you check that the cross bolt is unengraved? I should have expected it to be engraved (and timed - ie. properly horizontal, not at an angle). If you can post some more pictures, that might help. Even quite ordinary guns were/ are engraved in a house style. Just on the basis of the one picture, I am a little dubious that it is a Holland & Holland rifle at all: so far as I can see, the engraved description is in respect of the cartridge, not the rifle. Any rogue can engrave a spurious maker's name on the barrel.
(2) Check the throat of the barrel for cordite burn. If there is any, either beat the price down or walk away.
I'll post some pictures of my H&H tomorrow, if I have time. My rifle is from the late '60s, and - frankly - it's a bit of a dog. The QD scope mounts do not align with the barrel and the stock is so badly fitted that the rifle kicks like a mule. Post-war H&H rifles were of variable quality; don't be seduced by the name alone.