I think the DSL100H power tubes are chassis mounted, but the pots and preamp tubes remain PCB mounted like on the original DSL100. The 100H isn't made in England, but otherwise I thought they were suppose to sound the same and have the same features.
From what I remember sound-wise it's the same amp aside from that resonance knob in place of the stupid Deep switch. Less ribbon cable and tubes are socket mounted. Made in China but that doesn't mean bad these days. Too much length in time from when I had a JCM 2000 DSL and played a new DSL 100H so I take what I say about comparing their tones with a grain of salt.