Hmm, wasn't the V1 that DJH markets now actually originated by Piercy Models? They are certainly listed separately on the
DJH website and they certainly look to be of a higher standard than Model Loco's
UK output. I've only ever seen one of their B1s close too (Bob Alderman built it) and this looked very much better than anything I've seen from DJH in 4mm and in much of their 7mm range.
The 4mm S15 is a bit of a disaster area, as Peter suggests, their U/N/U1/N1 is also 'interesting' - a friend is reconstructing bits from one into a rebuilt River - and there are certainly quite major dimensional problems with other examples in the 4mm range (which even Tony Wright, the great proselytiser for the range admits about some of the LNER pacifics) but it may not be reasonable to make this particular comparison. I freely admit to knowing nothing about this particular prototype, however. From what I can see above, the platework on the ACE model looks good; I'm less than convinced by what I can see of the rest of it, particularly the chimney and dome.
Adam