I know Dreams bed shop use these, not sure who makes them though? They have wheel tubs and a very low floor on the bottom deck.
I can’t help you with who makes them, but I used to do some work for some waste company doing medical waste in dustbins and the trailers were double deck twin axle jobs, they would actually sit on the ground if you dumped the air. Only 1" of a lip from pavement onto the bottom deck. they had barn doors and a taillift above them. I believe these are the same as Some Tesco pull around, if you look for a White double decker with a Tesco unit pulling it 
They have the large wheels, not the small twins. 
Hope this helps.
As I recall DPD (http://www.dpd.co.uk) use twin deck, tri axle trailers, where the upper deck is electrically raised and lowered.
I could be wrong, but I thought Cartwright made them. (http://www.cartwright-group.co.uk)
several manufacturers make them, Talson, Gray & Adams, van Eck, just off the top of my head. I actually knew where there were some second hand (2007) G&A for sale last month, if you would like me to find if they’re still available and full spec send me a pm.
We use Gray Adams double deck fridge trailers. Step frame design, 2/3 length lower deck, full length top deck. The deck is raised electrically and they have barn doors on the back. They look pretty much the same as the tesco ones. They run on small wheels put all dualed.
tofer:
We use Gray Adams double deck fridge trailers. Step frame design, 2/3 length lower deck, full length top deck. The deck is raised electrically and they have barn doors on the back. They look pretty much the same as the tesco ones. They run on small wheels put all dualed.
They will never be as low as one running on big singles with independent suspension units, simply because an axle is still required for small wheel twins.
Certainly Talson and I believe van Eck also, can offer both decks able to take 1830mm tall roll cages within a 4 metre overall height. Something which is not physically possible with small wheels and a standard axle and suspension set up.
acd1202:
tofer:
We use Gray Adams double deck fridge trailers. Step frame design, 2/3 length lower deck, full length top deck. The deck is raised electrically and they have barn doors on the back. They look pretty much the same as the tesco ones. They run on small wheels put all dualed.They will never be as low as one running on big singles with independent suspension units, simply because an axle is still required for small wheel twins.
Certainly Talson and I believe van Eck also, can offer both decks able to take 1830mm tall roll cages within a 4 metre overall height. Something which is not physically possible with small wheels and a standard axle and suspension set up.
I don’t think I’ve seen any of those. I’ll be looking for them now 
emonscargo.com/cargo/upload/ … n_2win.jpg
A picture of said Talson 4 metre double deck as operated by Emons Corgo, you do see them in the UK.
The CityLink double deck G&A boxes also use the independent suspension units and super singles, but they don’t run them as low as this.
Thanks all
W trailers keighley