  We report the discovery of 76 new T dwarfs from the UKIDSS Large Area Survey
(LAS). Near-infrared broad and narrow-band photometry and spectroscopy are
presented for the new objects, along with WISE and warm-Spitzer photometry.
Proper motions for 128 UKIDSS T dwarfs are presented from a new two epoch LAS
proper motion catalogue. We use these motions to identify two new benchmark
systems: LHS 6176AB, a T8+M4 pair and HD118865AB, a T5.5+F8 pair. Using age
constraints from the primaries and evolutionary models to constrain the radii
we have estimated their physical properties from their bolometric luminosity.
We compare the colours and properties of known benchmark T dwarfs to the latest
model atmospheres and draw two principal conclusions. Firstly, it appears that
the H - [4.5] and J - W2 colours are more sensitive to metallicity than has
previously been recognised, such that differences in metallicity may dominate
over differences in Teff when considering relative properties of cool objects
using these colours. Secondly, the previously noted apparent dominance of young
objects in the late-T dwarf sample is no longer apparent when using the new
model grids and the expanded sample of late-T dwarfs and benchmarks. This is
supported by the apparently similar distribution of late-T dwarfs and
earlier-type T dwarfs on reduced proper motion diagrams that we present.
Finally, we present updated space densities for the late-T dwarfs, and compare
our values to simulation predictions and those from WISE.
