  Aims: Detect tertiary components of close binaries from spectroscopy and
light curve modelling; investigate light-travel time effect and the possibility
of magnetic activity cycles; measure mass-ratios for unstudied systems and
derive absolute parameters.
  Methods: We carried out new photometric and spectroscopic observations of
five bright (V<10.5 mag) close eclipsing binaries, predominantly in the
southern skies. We obtained full Johnson BV light curves, which were modelled
with the Wilson-Devinney code. Radial velocities were measured with the
cross-correlation method using IAU radial velocity standards as spectral
templates. Period changes were studied with the O-C method, utilising published
epochs of minimum light (XY Leo) and ASAS photometry (VZ Lib).
  Results: For three objects (DX Tuc, QY Hya, V870 Ara), absolute parameters
have been determined for the first time. We detect spectroscopically the
tertiary components in XY Leo, VZ Lib and discover one in QY Hya. For XY Leo we
update the light-time effect parameters and detect a secondary periodicity of
about 5100 d in the O$-$C diagram that may hint about the existence of
short-period magnetic cycles. A combination of recent photometric data shows
that the orbital period of the tertiary star in VZ Lib is likely to be over
1500 d. QY Hya is a semi-detached X-ray active binary in a triple system with K
and M-type components, while V870 Ara is a contact binary with the third
smallest spectroscopic mass-ratio for a W UMa star to date (q=0.082+/-0.030).
This small mass-ratio, being close to the theoretical minimum for contact
binaries, suggests that V870 Ara has the potential of constraining evolutionary
scenarios of binary mergers. The inferred distances to these systems are
compatible with the Hipparcos parallaxes.
