Got some more rolling stock legroom dimensions today, and very interesting it is. I have added all this to the first post.
Class 158 East Midland Trains (refurbished)
Standard = 29" / Priority = 31+" / First = N/A
Class 220/221 Voyager Cross Country
Standard = 28" / Priority = 33" / First = ?
Class 222 Meridian East Midland Trains
Standard = 29+" / Priority = 31+" / First = 36+"
Class 390 Pendolino Virgin
Standard = 29 to 30" / Priority = 31+" / First = 35 to 36"
For modern trains all the legroom is reasonable to good, apart from Voyagers, obviously.
The refurbished EMT C158s are arguably deserved of special praise because the original C158s were so poor as far as legroom on medium/long distance stock is concerned. EMT can go to the top of the class as far as I'm concerned for resisting the temptation to pack as many seats in as possible. Some standard seats actually had 30" of leg room, I had to keep checking I wasn't actually in the priority seats ! The only thing I dislike are the high backed seats, but overall, very good.
Although the joined up high backed seats and the wide window pillars on the Meridians tends to make them a bit claustrophobic the leg room is fine, it's significantly better than a Voyager, so credit to MML who, I assume, specified the seat spacings.
Voyagers ? Standard seat legroom, for a long distance train, is poor, but "priority" leg room is very generous indeed. It really is no surprise that those "in the know" always go for the priority seats. The disparity between normal standard and priority standard is a huge 5".
Pendolinos ? They may have ridiculously small windows but nobody can complain about the leg room. Whether the seat spacing was forced on Virgin or not, the legroom, for modern stock, is generous. Note, I'm unbiased in my view here, and not afraid to publicise data, good or bad.
All this throws into sharp focus just how bad the Mk4 Mallard stock is for (standard) legroom, at 27". When I get a chance I'll recheck that data, but it isn't going to be that far out, at best it'll only be the same as a Voyager.