I had a problem with my g/c guitar hg where the trompete was too loud, maybe because the top was thin in that area. Under advice from the maker, it was solved by glueing a 1" square 3mm thick piece of sycamore wood under that spot.
To do this a small hole was drilled in top in the slot of the trompette/mouche bridge, where it would not be seen. A piece of strong linen thread was fed down through this hole and out through the soundhole.The square of wood for the repair had a hole in the center, the thread went through this with a knot at the back, I put some Titebond glue on the wood square, put it through the soundhole and pulled it up under the trompette bridge, holding tight for five-ten minutes. It really helped, that instrument still really 'sings' on the chanterelles, but is now more balanced on the trompette volume.
Maybe you could do something similar under your main bridge?
Back to the topic of older British HG's, I know someone who has a Warrington and will ask for pics.