  We present the first detailed analysis of the mass and dynamical structure of
a sample of six early-type lens galaxies, selected from the Sloan Lens ACS
Survey, in the redshift range 0.08 < z < 0.33. Both Hubble Space Telescope
(HST)/ACS high-resolution imaging and VLT VIMOS integral field spectroscopy are
available for these systems. The galaxies are modelled - under the assumptions
of axial symmetry and two-integral stellar distribution function - by making
use of the CAULDRON code, which self-consistently combines gravitational
lensing and stellar dynamics, and is fully embedded within the framework of
Bayesian statistics. The principal results of this study are: (i) all galaxies
in the sample are well described by a simple axisymmetric power-law profile for
the total density, with a logarithmic slope gamma very close to isothermal
(<gamma> = 1.98 +/- 0.05 and an intrinsic spread close to 5 per cent) showing
no evidence of evolution over the probed range of redshift; (ii) the axial
ratio of the total density distribution is rounder than 0.65 and in all cases,
except for a fast rotator, does not deviate significantly from the flattening
of the intrinsic stellar distribution; (iii) the dark matter fraction within
the effective radius has a lower limit of about 15 to 30 per cent; (iv) the
sample galaxies are only mildly anisotropic, with delta <= 0.16; (v) the
physical distinction among slow and fast rotators, quantified by the v/sigma
ratio and the intrinsic angular momentum, is already present at z > 0.1.
Altogether, early-type galaxies at z = 0.08 - 0.33 are found to be markedly
smooth and almost isothermal systems, structurally and dynamically very similar
to their nearby counterparts. (Abridged)
